rustc: support clang-based stdenv

Previously, we were passing `cc` and `c++` all the time to rustc bootstrap process.

This was wrong because `cc-rs` relies on the name of the compiler to detect whether this is Clang or a GNU GCC.

Related:

[1]: https://github.com/rust-lang/cc-rs/blob/df2f86ceafbe787698b890a3d6bde9f969d5fa88/src/lib.rs#L3334
[2]: https://rust-lang.zulipchat.com/#narrow/stream/122651-general/topic/Missing.20dynamic.20libraries.20when.20bootstrapping.20Rust/near/377914373

1 files changed, 9 insertions, 6 deletions

diff --git a/pkgs/development/compilers/rust/rustc.nix b/pkgs/development/compilers/rust/rustc.nix
index 869dd15df0be..774855c5c170 100644
--- a/pkgs/development/compilers/rust/rustc.nix
+++ b/pkgs/development/compilers/rust/rustc.nix
@@ -66,15 +66,18 @@ in stdenv.mkDerivation rec {
   # We need rust to build rust. If we don't provide it, configure will try to download it.
   # Reference: https://github.com/rust-lang/rust/blob/master/src/bootstrap/configure.py
   configureFlags = let
+    prefixForStdenv = stdenv: "${stdenv.cc}/bin/${stdenv.cc.targetPrefix}";
+    ccPrefixForStdenv = stdenv: "${prefixForStdenv stdenv}${if (stdenv.cc.isClang or false) then "clang" else "cc"}";
+    cxxPrefixForStdenv = stdenv: "${prefixForStdenv stdenv}${if (stdenv.cc.isClang or false) then "clang++" else "c++"}";
     setBuild  = "--set=target.${rust.toRustTarget stdenv.buildPlatform}";
     setHost   = "--set=target.${rust.toRustTarget stdenv.hostPlatform}";
     setTarget = "--set=target.${rust.toRustTarget stdenv.targetPlatform}";
-    ccForBuild  = "${pkgsBuildBuild.targetPackages.stdenv.cc}/bin/${pkgsBuildBuild.targetPackages.stdenv.cc.targetPrefix}cc";
-    cxxForBuild = "${pkgsBuildBuild.targetPackages.stdenv.cc}/bin/${pkgsBuildBuild.targetPackages.stdenv.cc.targetPrefix}c++";
-    ccForHost  = "${pkgsBuildHost.targetPackages.stdenv.cc}/bin/${pkgsBuildHost.targetPackages.stdenv.cc.targetPrefix}cc";
-    cxxForHost = "${pkgsBuildHost.targetPackages.stdenv.cc}/bin/${pkgsBuildHost.targetPackages.stdenv.cc.targetPrefix}c++";
-    ccForTarget  = "${pkgsBuildTarget.targetPackages.stdenv.cc}/bin/${pkgsBuildTarget.targetPackages.stdenv.cc.targetPrefix}cc";
-    cxxForTarget = "${pkgsBuildTarget.targetPackages.stdenv.cc}/bin/${pkgsBuildTarget.targetPackages.stdenv.cc.targetPrefix}c++";
+    ccForBuild  = ccPrefixForStdenv pkgsBuildBuild.targetPackages.stdenv;
+    cxxForBuild  = cxxPrefixForStdenv pkgsBuildBuild.targetPackages.stdenv;
+    ccForHost  = ccPrefixForStdenv pkgsBuildHost.targetPackages.stdenv;
+    cxxForHost  = cxxPrefixForStdenv pkgsBuildHost.targetPackages.stdenv;
+    ccForTarget  = ccPrefixForStdenv pkgsBuildTarget.targetPackages.stdenv;
+    cxxForTarget  = cxxPrefixForStdenv pkgsBuildTarget.targetPackages.stdenv;
   in [
     "--release-channel=stable"
     "--set=build.rustc=${rustc}/bin/rustc"