Remove unneeded overlay & fix devShell and build documentation

Author: docprofsky

README.md

@@ -18,15 +18,15 @@ things. So I made one.
 Building
 ========
 
-Running `nix-shell --command 'cargo build --release'` should work. The
+Running `nix develop --command cargo build --release` should work. The
 executable will then be in `./target/release/scromble`. Please file an
 issue if that doesn't work!
 
 If you would like to use the AVX2 backend for XChaCha20, build with
-`nix-shell --command 'RUSTFLAGS="-Ctarget-cpu=haswell
--Ctarget-feature=+sse2" cargo build --release'` instead. Everything
-else should be the same. The fastest results I've seen are expected
-with `RUSTFLAGS="-Ctarget-cpu=native"`.
+`RUSTFLAGS="-Ctarget-cpu=haswell -Ctarget-feature=+sse2" nix develop
+--command cargo build --release` instead. Everything else should be the
+same. The fastest results I've seen are expected with
+`RUSTFLAGS="-Ctarget-cpu=native"`.
 
 NOTE FOR WINDOWS USERS
 ======================

flake.lock

@@ -4,25 +4,19 @@
   inputs = {
     nixpkgs.url      = github:nixos/nixpkgs/nixos-24.11;
     flake-utils.url  = github:numtide/flake-utils;
-    rust-overlay.url = github:oxalica/rust-overlay;
   };
 
-  outputs = { self, nixpkgs, flake-utils, rust-overlay, ... }:
+  outputs = { self, nixpkgs, flake-utils, ... }:
     flake-utils.lib.eachDefaultSystem (system:
       let
-        overlays = [ (import rust-overlay) ];
         pkgs = import nixpkgs {
-          inherit system overlays;
+          inherit system;
         };
       in
       with pkgs;
       rec {
         devShell = mkShell {
-          buildInputs = [
-            openssl
-            pkgconfig
-            rust-bin.stable.latest.default
-          ];
+          buildInputs = [ cargo ];
 
           RUST_BACKTRACE="full";
         };