haskell.compiler.ghc94: don't roundtrip C compilation via assembly

pkgs/development/compilers/ghc/common-make-native-bignum.nix

@@ -364,7 +364,44 @@ stdenv.mkDerivation (
           else
             ./Cabal-3.2-3.4-paths-fix-cycle-aarch64-darwin.patch
         )
-      ];
+      ]
+      # Before GHC 9.6, GHC, when used to compile C sources (i.e. to drive the CC), would first
+      # invoke the C compiler to generate assembly and later call the assembler on the result of
+      # that operation. Unfortunately, that is brittle in a lot of cases, e.g. when using mismatched
+      # CC / assembler (https://gitlab.haskell.org/ghc/ghc/-/merge_requests/12005). This issue
+      # does not affect us. However, LLVM 18 introduced a check in clang that makes sure no
+      # non private labels occur between .cfi_startproc and .cfi_endproc which causes the
+      # assembly that the same version (!) of clang generates from rts/StgCRun.c to be rejected.
+      # This causes GHC to fail compilation on mach-o platforms ever since we upgraded to
+      # LLVM 19.
+      #
+      # clang compiles the same file without issues whithout the roundtrip via assembly. Thus,
+      # the solution is to backport those changes from GHC 9.6 that skip the intermediate
+      # assembly step.
+      #
+      # https://gitlab.haskell.org/ghc/ghc/-/issues/25608#note_622589
+      # https://gitlab.haskell.org/ghc/ghc/-/merge_requests/6877
+      ++ (
+        if lib.versionAtLeast version "9.4" then
+          [
+            # Need to use this patch so the next one applies, passes file location info to the cc phase
+            (fetchpatch {
+              name = "ghc-add-location-to-cc-phase.patch";
+              url = "https://gitlab.haskell.org/ghc/ghc/-/commit/4a7256a75af2fc0318bef771a06949ffb3939d5a.patch";
+              hash = "sha256-DnTI+i1zMebeWvw75D59vMaEEBb2Nr9HusxTyhmdy2M=";
+            })
+            # Makes Cc phase directly generate object files instead of assembly
+            (fetchpatch {
+              name = "ghc-cc-directly-emit-object.patch";
+              url = "https://gitlab.haskell.org/ghc/ghc/-/commit/96811ba491495b601ec7d6a32bef8563b0292109.patch";
+              hash = "sha256-G8u7/MK/tGOEN8Wxccxj/YIOP7mL2G9Co1WKdHXOo6I=";
+            })
+          ]
+        else
+          [
+            # TODO(@sternenseemann): backport changes to GHC < 9.4 if possible
+          ]
+      );
 
     postPatch = "patchShebangs .";