let
              musl-gcc = inputs.nixpkgs.lib.systems.elaborate "x86_64-unknown-linux-musl";
              musl-llvm = inputs.nixpkgs.lib.recursiveUpdate musl-gcc {
                useLLVM = true;
                linker = "lld";
                config = "x86_64-unknown-linux-musl";
              };
            in
              {
                nixpkgs.buildPlatform = musl-llvm;
                nixpkgs.hostPlatform = musl-llvm;
              }

fetching git input 'git+file:///home/grimmauld/musl-vm'
error:
       … while calling the 'seq' builtin
         at /nix/store/dndmsb8w6cxy8qncmkigdy2pii16j07x-nixpkgs-patched/lib/modules.nix:361:18:
          360|         options = checked options;
          361|         config = checked (removeAttrs config [ "_module" ]);
             |                  ^
          362|         _module = checked (config._module);

       … while evaluating the attribute 'unmatchedDefns'
         at /nix/store/dndmsb8w6cxy8qncmkigdy2pii16j07x-nixpkgs-patched/lib/modules.nix:894:7:
          893|       # Transforms unmatchedDefnsByName into a list of definitions
          894|       unmatchedDefns =
             |       ^
          895|         if configs == [ ] then

       (stack trace truncated; use '--show-trace' to show the full trace)

       error: attribute 'version' missing
       at /nix/store/dndmsb8w6cxy8qncmkigdy2pii16j07x-nixpkgs-patched/pkgs/stdenv/linux/default.nix:560:51:
          559|             pname = prevStage.bintools.bintools.pname + "-patchelfed-ld";
          560|             inherit (prevStage.bintools.bintools) version;
             |                                                   ^
          561|             passthru = { inherit (prevStage.bintools.passthru) isFromBootstrapFiles; };

diff --git a/pkgs/build-support/rust/lib/default.nix b/pkgs/build-support/rust/lib/default.nix
index e492d03e3026..a5769e761294 100644
--- a/pkgs/build-support/rust/lib/default.nix
+++ b/pkgs/build-support/rust/lib/default.nix
@@ -74,7 +74,7 @@
       # pkgsTargetTarget.stdenv.cc is often simply wrong.  We must omit
       # the following lines when rustTargetPlatform collides with
       # rustHostPlatform.
-      + lib.optionalString (rustTargetPlatform != rustHostPlatform) ''
+      + lib.optionalString (stdenv.hostPlatform != stdenv.targetPlatform) ''
         "CC_${stdenv.targetPlatform.rust.cargoEnvVarTarget}=${ccForTarget}" \
         "CXX_${stdenv.targetPlatform.rust.cargoEnvVarTarget}=${cxxForTarget}" \
         "CARGO_TARGET_${stdenv.targetPlatform.rust.cargoEnvVarTarget}_LINKER=${ccForTarget}" \