diff --git a/pkgs/by-name/hp/hplip/package.nix b/pkgs/by-name/hp/hplip/package.nix
index 5b75315c16e79..524b241734f1f 100644
--- a/pkgs/by-name/hp/hplip/package.nix
+++ b/pkgs/by-name/hp/hplip/package.nix
@@ -72,12 +72,6 @@ let
 
 in
 
-assert
-  withPlugin
-  ->
-    builtins.elem hplipArch pluginArches
-    || throw "HPLIP plugin not supported on ${stdenv.hostPlatform.system}";
-
 python3Packages.buildPythonApplication {
   inherit pname version;
   format = "other";
@@ -361,13 +355,7 @@ python3Packages.buildPythonApplication {
           bsd2
           gpl2Plus
         ];
-    platforms = [
-      "i686-linux"
-      "x86_64-linux"
-      "armv6l-linux"
-      "armv7l-linux"
-      "aarch64-linux"
-    ];
+    platforms = lib.attrNames hplipPlatforms;
     maintainers = with maintainers; [ ttuegel ];
   };
 }
diff --git a/pkgs/development/androidndk-pkgs/androidndk-pkgs.nix b/pkgs/development/androidndk-pkgs/androidndk-pkgs.nix
index 513ca78f0a977..d66ce006fdb99 100644
--- a/pkgs/development/androidndk-pkgs/androidndk-pkgs.nix
+++ b/pkgs/development/androidndk-pkgs/androidndk-pkgs.nix
@@ -1,4 +1,5 @@
 {
+  config,
   lib,
   stdenv,
   makeWrapper,
@@ -21,7 +22,7 @@ let
   # some builds need that clarity.
   #
   ndkBuildInfoFun =
-    { config, ... }:
+    fallback:
     {
       x86_64-apple-darwin = {
         double = "darwin-x86_64";
@@ -30,10 +31,10 @@ let
         double = "linux-x86_64";
       };
     }
-    .${config} or (throw "Android NDK doesn't support building on ${config}, as far as we know");
+    .${stdenv.buildPlatform.config} or fallback;
 
   ndkTargetInfoFun =
-    { config, ... }:
+    fallback:
     {
       i686-unknown-linux-android = {
         triple = "i686-linux-android";
@@ -52,10 +53,14 @@ let
         triple = "aarch64-linux-android";
       };
     }
-    .${config} or (throw "Android NDK doesn't support targetting ${config}, as far as we know");
+    .${stdenv.targetPlatform.config} or fallback;
 
-  buildInfo = ndkBuildInfoFun stdenv.buildPlatform;
-  targetInfo = ndkTargetInfoFun stdenv.targetPlatform;
+  buildInfo = ndkBuildInfoFun (
+    throw "Android NDK doesn't support building on ${stdenv.buildPlatform.config}, as far as we know"
+  );
+  targetInfo = ndkTargetInfoFun (
+    throw "Android NDK doesn't support targetting ${stdenv.targetPlatform.config}, as far as we know"
+  );
 
   androidSdkVersion =
     if
@@ -74,119 +79,123 @@ let
   );
 in
 
-lib.recurseIntoAttrs rec {
-  # Misc tools
-  binaries = stdenv.mkDerivation {
-    pname = "${targetPrefix}ndk-toolchain";
-    inherit (androidndk) version;
-    nativeBuildInputs = [
-      makeWrapper
-      autoPatchelfHook
-    ];
-    propagatedBuildInputs = [ androidndk ];
-    passthru = {
-      inherit targetPrefix;
-      isClang = true; # clang based cc, but bintools ld
-      inherit (llvmPackages.clang.cc) hardeningUnsupportedFlagsByTargetPlatform;
+if !config.allowAliases && (ndkBuildInfoFun null == null || ndkTargetInfoFun null == null) then
+  # Don't throw without aliases to not break CI.
+  null
+else
+  lib.recurseIntoAttrs rec {
+    # Misc tools
+    binaries = stdenv.mkDerivation {
+      pname = "${targetPrefix}ndk-toolchain";
+      inherit (androidndk) version;
+      nativeBuildInputs = [
+        makeWrapper
+        autoPatchelfHook
+      ];
+      propagatedBuildInputs = [ androidndk ];
+      passthru = {
+        inherit targetPrefix;
+        isClang = true; # clang based cc, but bintools ld
+        inherit (llvmPackages.clang.cc) hardeningUnsupportedFlagsByTargetPlatform;
+      };
+      dontUnpack = true;
+      dontBuild = true;
+      dontStrip = true;
+      dontConfigure = true;
+      dontPatch = true;
+      autoPatchelfIgnoreMissingDeps = true;
+      installPhase = ''
+        # https://developer.android.com/ndk/guides/other_build_systems
+        mkdir -p $out
+        cp -r ${androidndk}/libexec/android-sdk/ndk-bundle/toolchains/llvm/prebuilt/${buildInfo.double} $out/toolchain
+        find $out/toolchain -type d -exec chmod 777 {} \;
+
+        if [ ! -d $out/toolchain/sysroot/usr/lib/${targetInfo.triple}/${androidSdkVersion} ]; then
+          echo "NDK does not contain libraries for SDK version ${androidSdkVersion}";
+          exit 1
+        fi
+
+        ln -vfs $out/toolchain/sysroot/usr/lib $out/lib
+        ln -s $out/toolchain/sysroot/usr/lib/${targetInfo.triple}/*.so $out/lib/
+        ln -s $out/toolchain/sysroot/usr/lib/${targetInfo.triple}/*.a $out/lib/
+        chmod +w $out/lib/*
+        ln -s $out/toolchain/sysroot/usr/lib/${targetInfo.triple}/${androidSdkVersion}/*.so $out/lib/
+        ln -s $out/toolchain/sysroot/usr/lib/${targetInfo.triple}/${androidSdkVersion}/*.o $out/lib/
+
+        echo "INPUT(-lc++_static)" > $out/lib/libc++.a
+
+        ln -s $out/toolchain/bin $out/bin
+        ln -s $out/toolchain/${targetInfo.triple}/bin/* $out/bin/
+        for f in $out/bin/${targetInfo.triple}-*; do
+          ln -s $f ''${f/${targetInfo.triple}-/${targetPrefix}}
+        done
+        for f in $(find $out/toolchain -type d -name ${targetInfo.triple}); do
+          ln -s $f ''${f/${targetInfo.triple}/${targetPrefix}}
+        done
+
+        rm -f $out/bin/${targetPrefix}ld
+        ln -s $out/bin/lld $out/bin/${targetPrefix}ld
+
+        (cd $out/bin;
+          for tool in llvm-*; do
+            ln -sf $tool ${targetPrefix}$(echo $tool | sed 's/llvm-//')
+            ln -sf $tool $(echo $tool | sed 's/llvm-//')
+          done)
+
+        ln -sf $out/bin/yasm $out/bin/${targetPrefix}as
+        ln -sf $out/bin/yasm $out/bin/as
+
+        patchShebangs $out/bin
+      '';
+      meta = {
+        description = "The Android NDK toolchain, tuned for other platforms";
+        license = with lib.licenses; [ unfree ];
+        teams = [ lib.teams.android ];
+      };
     };
-    dontUnpack = true;
-    dontBuild = true;
-    dontStrip = true;
-    dontConfigure = true;
-    dontPatch = true;
-    autoPatchelfIgnoreMissingDeps = true;
-    installPhase = ''
-      # https://developer.android.com/ndk/guides/other_build_systems
-      mkdir -p $out
-      cp -r ${androidndk}/libexec/android-sdk/ndk-bundle/toolchains/llvm/prebuilt/${buildInfo.double} $out/toolchain
-      find $out/toolchain -type d -exec chmod 777 {} \;
-
-      if [ ! -d $out/toolchain/sysroot/usr/lib/${targetInfo.triple}/${androidSdkVersion} ]; then
-        echo "NDK does not contain libraries for SDK version ${androidSdkVersion}";
-        exit 1
-      fi
-
-      ln -vfs $out/toolchain/sysroot/usr/lib $out/lib
-      ln -s $out/toolchain/sysroot/usr/lib/${targetInfo.triple}/*.so $out/lib/
-      ln -s $out/toolchain/sysroot/usr/lib/${targetInfo.triple}/*.a $out/lib/
-      chmod +w $out/lib/*
-      ln -s $out/toolchain/sysroot/usr/lib/${targetInfo.triple}/${androidSdkVersion}/*.so $out/lib/
-      ln -s $out/toolchain/sysroot/usr/lib/${targetInfo.triple}/${androidSdkVersion}/*.o $out/lib/
-
-      echo "INPUT(-lc++_static)" > $out/lib/libc++.a
-
-      ln -s $out/toolchain/bin $out/bin
-      ln -s $out/toolchain/${targetInfo.triple}/bin/* $out/bin/
-      for f in $out/bin/${targetInfo.triple}-*; do
-        ln -s $f ''${f/${targetInfo.triple}-/${targetPrefix}}
-      done
-      for f in $(find $out/toolchain -type d -name ${targetInfo.triple}); do
-        ln -s $f ''${f/${targetInfo.triple}/${targetPrefix}}
-      done
-
-      rm -f $out/bin/${targetPrefix}ld
-      ln -s $out/bin/lld $out/bin/${targetPrefix}ld
 
-      (cd $out/bin;
-        for tool in llvm-*; do
-          ln -sf $tool ${targetPrefix}$(echo $tool | sed 's/llvm-//')
-          ln -sf $tool $(echo $tool | sed 's/llvm-//')
-        done)
-
-      ln -sf $out/bin/yasm $out/bin/${targetPrefix}as
-      ln -sf $out/bin/yasm $out/bin/as
-
-      patchShebangs $out/bin
-    '';
-    meta = {
-      description = "The Android NDK toolchain, tuned for other platforms";
-      license = with lib.licenses; [ unfree ];
-      teams = [ lib.teams.android ];
+    binutils = wrapBintoolsWith {
+      bintools = binaries;
+      libc = targetAndroidndkPkgs.libraries;
     };
-  };
 
-  binutils = wrapBintoolsWith {
-    bintools = binaries;
-    libc = targetAndroidndkPkgs.libraries;
-  };
-
-  clang = wrapCCWith {
-    cc = binaries // {
-      # for packages expecting libcompiler-rt, etc. to come from here (stdenv.cc.cc.lib)
-      lib = targetAndroidndkPkgs.libraries;
+    clang = wrapCCWith {
+      cc = binaries // {
+        # for packages expecting libcompiler-rt, etc. to come from here (stdenv.cc.cc.lib)
+        lib = targetAndroidndkPkgs.libraries;
+      };
+      bintools = binutils;
+      libc = targetAndroidndkPkgs.libraries;
+      extraBuildCommands = ''
+        echo "-D__ANDROID_API__=${stdenv.targetPlatform.androidSdkVersion}" >> $out/nix-support/cc-cflags
+        # Android needs executables linked with -pie since version 5.0
+        # Use -fPIC for compilation, and link with -pie if no -shared flag used in ldflags
+        echo "-target ${targetInfo.triple} -fPIC" >> $out/nix-support/cc-cflags
+        echo "-z,noexecstack -z,relro -z,now -z,muldefs" >> $out/nix-support/cc-ldflags
+        echo 'expandResponseParams "$@"' >> $out/nix-support/add-flags.sh
+        echo 'if [[ ! (" ''${params[@]} " =~ " -shared ") && ! (" ''${params[@]} " =~ " -no-pie ") ]]; then NIX_LDFLAGS_${suffixSalt}+=" -pie"; fi' >> $out/nix-support/add-flags.sh
+        echo "-Xclang -mnoexecstack" >> $out/nix-support/cc-cxxflags
+        if [ ${targetInfo.triple} == arm-linux-androideabi ]; then
+          # https://android.googlesource.com/platform/external/android-cmake/+/refs/heads/cmake-master-dev/android.toolchain.cmake
+          echo "--fix-cortex-a8" >> $out/nix-support/cc-ldflags
+        fi
+      '';
     };
-    bintools = binutils;
-    libc = targetAndroidndkPkgs.libraries;
-    extraBuildCommands = ''
-      echo "-D__ANDROID_API__=${stdenv.targetPlatform.androidSdkVersion}" >> $out/nix-support/cc-cflags
-      # Android needs executables linked with -pie since version 5.0
-      # Use -fPIC for compilation, and link with -pie if no -shared flag used in ldflags
-      echo "-target ${targetInfo.triple} -fPIC" >> $out/nix-support/cc-cflags
-      echo "-z,noexecstack -z,relro -z,now -z,muldefs" >> $out/nix-support/cc-ldflags
-      echo 'expandResponseParams "$@"' >> $out/nix-support/add-flags.sh
-      echo 'if [[ ! (" ''${params[@]} " =~ " -shared ") && ! (" ''${params[@]} " =~ " -no-pie ") ]]; then NIX_LDFLAGS_${suffixSalt}+=" -pie"; fi' >> $out/nix-support/add-flags.sh
-      echo "-Xclang -mnoexecstack" >> $out/nix-support/cc-cxxflags
-      if [ ${targetInfo.triple} == arm-linux-androideabi ]; then
-        # https://android.googlesource.com/platform/external/android-cmake/+/refs/heads/cmake-master-dev/android.toolchain.cmake
-        echo "--fix-cortex-a8" >> $out/nix-support/cc-ldflags
+
+    # Bionic lib C and other libraries.
+    #
+    # We use androidndk from the previous stage, else we waste time or get cycles
+    # cross-compiling packages to wrap incorrectly wrap binaries we don't include
+    # anyways.
+    libraries = runCommand "bionic-prebuilt" { } ''
+      lpath=${buildAndroidndk}/libexec/android-sdk/ndk-bundle/toolchains/llvm/prebuilt/${buildInfo.double}/sysroot/usr/lib/${targetInfo.triple}/${androidSdkVersion}
+      if [ ! -d $lpath ]; then
+        echo "NDK does not contain libraries for SDK version ${androidSdkVersion} <$lpath>"
+        exit 1
       fi
+      mkdir -p $out/lib
+      cp $lpath/*.so $lpath/*.a $out/lib
+      chmod +w $out/lib/*
+      cp $lpath/* $out/lib
     '';
-  };
-
-  # Bionic lib C and other libraries.
-  #
-  # We use androidndk from the previous stage, else we waste time or get cycles
-  # cross-compiling packages to wrap incorrectly wrap binaries we don't include
-  # anyways.
-  libraries = runCommand "bionic-prebuilt" { } ''
-    lpath=${buildAndroidndk}/libexec/android-sdk/ndk-bundle/toolchains/llvm/prebuilt/${buildInfo.double}/sysroot/usr/lib/${targetInfo.triple}/${androidSdkVersion}
-    if [ ! -d $lpath ]; then
-      echo "NDK does not contain libraries for SDK version ${androidSdkVersion} <$lpath>"
-      exit 1
-    fi
-    mkdir -p $out/lib
-    cp $lpath/*.so $lpath/*.a $out/lib
-    chmod +w $out/lib/*
-    cp $lpath/* $out/lib
-  '';
-}
+  }
diff --git a/pkgs/development/androidndk-pkgs/default.nix b/pkgs/development/androidndk-pkgs/default.nix
index 3fd4b5f66527f..0b59c4a0d666e 100644
--- a/pkgs/development/androidndk-pkgs/default.nix
+++ b/pkgs/development/androidndk-pkgs/default.nix
@@ -24,7 +24,7 @@ let
       majorVersion = lib.versions.major ndkVersion;
     in
     import ./androidndk-pkgs.nix {
-      inherit lib;
+      inherit config lib;
       inherit (buildPackages)
         makeWrapper
         autoPatchelfHook
diff --git a/pkgs/development/interpreters/elixir/generic-builder.nix b/pkgs/development/interpreters/elixir/generic-builder.nix
index 4a15f07b3f583..680bc00b3ff6e 100644
--- a/pkgs/development/interpreters/elixir/generic-builder.nix
+++ b/pkgs/development/interpreters/elixir/generic-builder.nix
@@ -1,4 +1,5 @@
 {
+  config,
   lib,
   stdenv,
   fetchFromGitHub,
@@ -56,6 +57,8 @@ let
       true
     else
       versionOlder (versions.major (getVersion erlang)) maxShiftMajor;
+  minAssert = versionAtLeast (getVersion erlang) minimumOTPVersion;
+  bothAssert = minAssert && maxAssert;
 
   elixirShebang =
     if stdenv.hostPlatform.isDarwin then
@@ -69,73 +72,75 @@ let
 
   erlc_opts = [ "deterministic" ] ++ optionals debugInfo [ "debug_info" ];
 in
-assert assertMsg (versionAtLeast (getVersion erlang) minimumOTPVersion) compatibilityMsg;
-assert assertMsg maxAssert compatibilityMsg;
-
-stdenv.mkDerivation {
-  pname = "${baseName}";
-
-  inherit src version debugInfo;
-
-  nativeBuildInputs = [ makeWrapper ];
-  buildInputs = [ erlang ];
-
-  env = {
-    LANG = "C.UTF-8";
-    LC_TYPE = "C.UTF-8";
-    DESTDIR = placeholder "out";
-    PREFIX = "/";
-    ERL_COMPILER_OPTIONS = "[${concatStringsSep "," erlc_opts}]";
-  };
-
-  preBuild = ''
-    patchShebangs ${escriptPath} || true
-  '';
-
-  # copy stdlib source files for LSP access
-  postInstall = ''
-    for d in lib/*; do
-      cp -R "$d/lib" "$out/lib/elixir/$d"
-    done
-  '';
+if !config.allowAliases && !bothAssert then
+  # Don't throw without aliases to not break CI.
+  null
+else
+  assert assertMsg bothAssert compatibilityMsg;
+  stdenv.mkDerivation {
+    pname = "${baseName}";
+
+    inherit src version debugInfo;
+
+    nativeBuildInputs = [ makeWrapper ];
+    buildInputs = [ erlang ];
+
+    env = {
+      LANG = "C.UTF-8";
+      LC_TYPE = "C.UTF-8";
+      DESTDIR = placeholder "out";
+      PREFIX = "/";
+      ERL_COMPILER_OPTIONS = "[${concatStringsSep "," erlc_opts}]";
+    };
+
+    preBuild = ''
+      patchShebangs ${escriptPath} || true
+    '';
 
-  postFixup = ''
-    # Elixir binaries are shell scripts which run erl. Add some stuff
-    # to PATH so the scripts can run without problems.
-
-    for f in $out/bin/*; do
-      b=$(basename $f)
-      if [ "$b" = mix ]; then continue; fi
-      wrapProgram $f \
-        --prefix PATH ":" "${
-          lib.makeBinPath [
-            erlang
-            coreutils
-            curl
-            bash
-          ]
-        }"
-    done
-
-    substituteInPlace $out/bin/mix \
-      --replace "/usr/bin/env elixir" "${elixirShebang}"
-  '';
+    # copy stdlib source files for LSP access
+    postInstall = ''
+      for d in lib/*; do
+        cp -R "$d/lib" "$out/lib/elixir/$d"
+      done
+    '';
 
-  pos = builtins.unsafeGetAttrPos "sha256" args;
-  meta = with lib; {
-    homepage = "https://elixir-lang.org/";
-    description = "Functional, meta-programming aware language built on top of the Erlang VM";
-
-    longDescription = ''
-      Elixir is a functional, meta-programming aware language built on
-      top of the Erlang VM. It is a dynamic language with flexible
-      syntax and macro support that leverages Erlang's abilities to
-      build concurrent, distributed and fault-tolerant applications
-      with hot code upgrades.
+    postFixup = ''
+      # Elixir binaries are shell scripts which run erl. Add some stuff
+      # to PATH so the scripts can run without problems.
+
+      for f in $out/bin/*; do
+        b=$(basename $f)
+        if [ "$b" = mix ]; then continue; fi
+        wrapProgram $f \
+          --prefix PATH ":" "${
+            lib.makeBinPath [
+              erlang
+              coreutils
+              curl
+              bash
+            ]
+          }"
+      done
+
+      substituteInPlace $out/bin/mix \
+        --replace "/usr/bin/env elixir" "${elixirShebang}"
     '';
 
-    license = licenses.asl20;
-    platforms = platforms.unix;
-    teams = [ teams.beam ];
-  };
-}
+    pos = builtins.unsafeGetAttrPos "sha256" args;
+    meta = with lib; {
+      homepage = "https://elixir-lang.org/";
+      description = "Functional, meta-programming aware language built on top of the Erlang VM";
+
+      longDescription = ''
+        Elixir is a functional, meta-programming aware language built on
+        top of the Erlang VM. It is a dynamic language with flexible
+        syntax and macro support that leverages Erlang's abilities to
+        build concurrent, distributed and fault-tolerant applications
+        with hot code upgrades.
+      '';
+
+      license = licenses.asl20;
+      platforms = platforms.unix;
+      teams = [ teams.beam ];
+    };
+  }
diff --git a/pkgs/development/interpreters/lfe/generic-builder.nix b/pkgs/development/interpreters/lfe/generic-builder.nix
index 27d1c6d6c85d9..9501d712785de 100644
--- a/pkgs/development/interpreters/lfe/generic-builder.nix
+++ b/pkgs/development/interpreters/lfe/generic-builder.nix
@@ -1,4 +1,5 @@
 {
+  config,
   lib,
   fetchFromGitHub,
   erlang,
@@ -37,6 +38,8 @@ let
 
   mainVersion = versions.major (getVersion erlang);
 
+  maxAssert = versionAtLeast maximumOTPVersion mainVersion;
+
   proper = buildHex {
     name = "proper";
     version = "1.4.0";
@@ -45,82 +48,85 @@ let
   };
 
 in
-assert (assertMsg (versionAtLeast maximumOTPVersion mainVersion)) ''
-  LFE ${version} is supported on OTP <=${maximumOTPVersion}, not ${mainVersion}.
-'';
-
-buildRebar3 {
-  name = baseName;
-
-  inherit src version;
-
-  nativeBuildInputs = [
-    makeWrapper
-    erlang
-  ];
-  beamDeps = [ proper ];
-  patches = [
-    ./fix-rebar-config.patch
-    ./dedup-ebins.patch
-  ] ++ patches;
-  doCheck = true;
-  checkTarget = "travis";
-
-  makeFlags = [
-    "-e"
-    "MANDB=''"
-    "PREFIX=$$out"
-  ];
-
-  # These installPhase tricks are based on Elixir's Makefile.
-  # TODO: Make, upload, and apply a patch.
-  installPhase = optionalString (versionOlder version "1.3") ''
-    local libdir=$out/lib/lfe
-    local ebindir=$libdir/ebin
-    local bindir=$libdir/bin
-
-    rm -Rf $ebindir
-    install -m755 -d $ebindir
-    install -m644 _build/default/lib/lfe/ebin/* $ebindir
-
-    install -m755 -d $bindir
-
-    for bin in bin/lfe{,c,doc,script}; do install -m755 $bin $bindir; done
-
-    install -m755 -d $out/bin
-    for file in $bindir/*; do ln -sf $file $out/bin/; done
-  '';
-
-  # Thanks again, Elixir.
-  postFixup = ''
-    # LFE binaries are shell scripts which run erl and lfe.
-    # Add some stuff to PATH so the scripts can run without problems.
-    for f in $out/bin/*; do
-      wrapProgram $f \
-        --prefix PATH ":" "${
-          makeBinPath [
-            erlang
-            coreutils
-            bash
-          ]
-        }:$out/bin"
-      substituteInPlace $f --replace "/usr/bin/env" "${coreutils}/bin/env"
-    done
+if !config.allowAliases && !maxAssert then
+  # Don't throw without aliases to not break CI.
+  null
+else
+  assert assertMsg maxAssert ''
+    LFE ${version} is supported on OTP <=${maximumOTPVersion}, not ${mainVersion}.
   '';
-
-  meta = with lib; {
-    description = "Best of Erlang and of Lisp; at the same time!";
-    longDescription = ''
-      LFE, Lisp Flavoured Erlang, is a lisp syntax front-end to the Erlang
-      compiler. Code produced with it is compatible with "normal" Erlang
-      code. An LFE evaluator and shell is also included.
+  buildRebar3 {
+    name = baseName;
+
+    inherit src version;
+
+    nativeBuildInputs = [
+      makeWrapper
+      erlang
+    ];
+    beamDeps = [ proper ];
+    patches = [
+      ./fix-rebar-config.patch
+      ./dedup-ebins.patch
+    ] ++ patches;
+    doCheck = true;
+    checkTarget = "travis";
+
+    makeFlags = [
+      "-e"
+      "MANDB=''"
+      "PREFIX=$$out"
+    ];
+
+    # These installPhase tricks are based on Elixir's Makefile.
+    # TODO: Make, upload, and apply a patch.
+    installPhase = optionalString (versionOlder version "1.3") ''
+      local libdir=$out/lib/lfe
+      local ebindir=$libdir/ebin
+      local bindir=$libdir/bin
+
+      rm -Rf $ebindir
+      install -m755 -d $ebindir
+      install -m644 _build/default/lib/lfe/ebin/* $ebindir
+
+      install -m755 -d $bindir
+
+      for bin in bin/lfe{,c,doc,script}; do install -m755 $bin $bindir; done
+
+      install -m755 -d $out/bin
+      for file in $bindir/*; do ln -sf $file $out/bin/; done
     '';
 
-    homepage = "https://lfe.io";
-    downloadPage = "https://github.com/rvirding/lfe/releases";
+    # Thanks again, Elixir.
+    postFixup = ''
+      # LFE binaries are shell scripts which run erl and lfe.
+      # Add some stuff to PATH so the scripts can run without problems.
+      for f in $out/bin/*; do
+        wrapProgram $f \
+          --prefix PATH ":" "${
+            makeBinPath [
+              erlang
+              coreutils
+              bash
+            ]
+          }:$out/bin"
+        substituteInPlace $f --replace "/usr/bin/env" "${coreutils}/bin/env"
+      done
+    '';
 
-    license = licenses.asl20;
-    teams = [ teams.beam ];
-    platforms = platforms.unix;
-  };
-}
+    meta = with lib; {
+      description = "Best of Erlang and of Lisp; at the same time!";
+      longDescription = ''
+        LFE, Lisp Flavoured Erlang, is a lisp syntax front-end to the Erlang
+        compiler. Code produced with it is compatible with "normal" Erlang
+        code. An LFE evaluator and shell is also included.
+      '';
+
+      homepage = "https://lfe.io";
+      downloadPage = "https://github.com/rvirding/lfe/releases";
+
+      license = licenses.asl20;
+      teams = [ teams.beam ];
+      platforms = platforms.unix;
+    };
+  }
diff --git a/pkgs/top-level/all-packages.nix b/pkgs/top-level/all-packages.nix
index 1fe04076a1b9d..e4989833d5e12 100644
--- a/pkgs/top-level/all-packages.nix
+++ b/pkgs/top-level/all-packages.nix
@@ -5214,11 +5214,10 @@ with pkgs;
   # The GCC used to build libc for the target platform. Normal gccs will be
   # built with, and use, that cross-compiled libc.
   gccWithoutTargetLibc =
-    assert stdenv.targetPlatform != stdenv.hostPlatform;
     let
       libcCross1 = binutilsNoLibc.libc;
     in
-    wrapCCWith {
+    (wrapCCWith {
       cc = gccFun {
         # copy-pasted
         inherit noSysDirs;
@@ -5244,7 +5243,14 @@ with pkgs;
       bintools = binutilsNoLibc;
       libc = libcCross1;
       extraPackages = [ ];
-    };
+    }).overrideAttrs
+      (prevAttrs: {
+        meta = prevAttrs.meta // {
+          badPlatforms =
+            (prevAttrs.meta.badPlatforms or [ ])
+            ++ lib.optionals (stdenv.targetPlatform == stdenv.hostPlatform) [ stdenv.hostPlatform.system ];
+        };
+      });
 
   inherit (callPackage ../development/compilers/gcc/all.nix { inherit noSysDirs; })
     gcc9