rustc: Fix cross build for FreeBSD (#339909)

pkgs/development/compilers/rust/1_82.nix

@@ -20,6 +20,7 @@
   pkgsBuildTarget,
   pkgsBuildBuild,
   pkgsBuildHost,
+  pkgsHostTarget,
   pkgsTargetTarget,
   makeRustPlatform,
   wrapRustcWith,
@@ -40,7 +41,7 @@ let
         # Force LLVM to compile using clang + LLVM libs when targeting pkgsLLVM
         stdenv = pkgSet.stdenv.override {
           allowedRequisites = null;
-          cc = pkgSet.llvmPackages_18.clangUseLLVM;
+          cc = pkgSet.pkgsBuildHost.llvmPackages_18.clangUseLLVM;
         };
       }
     );
@@ -55,7 +56,7 @@ import ./default.nix
     llvmSharedForTarget = llvmSharedFor pkgsBuildTarget;
 
     # For use at runtime
-    llvmShared = llvmSharedFor { inherit llvmPackages_18 stdenv; };
+    llvmShared = llvmSharedFor pkgsHostTarget;
 
     # Expose llvmPackages used for rustc from rustc via passthru for LTO in Firefox
     llvmPackages =
@@ -74,7 +75,7 @@ import ./default.nix
               pkg.override {
                 stdenv = stdenv.override {
                   allowedRequisites = null;
-                  cc = llvmPackages.clangUseLLVM;
+                  cc = pkgsBuildHost.llvmPackages_18.clangUseLLVM;
                 };
               };
           in
@@ -87,7 +88,7 @@ import ./default.nix
             libcxx = llvmPackages.libcxx.override {
               stdenv = stdenv.override {
                 allowedRequisites = null;
-                cc = llvmPackages.clangNoLibcxx;
+                cc = pkgsBuildHost.llvmPackages_18.clangNoLibcxx;
                 hostPlatform = stdenv.hostPlatform // {
                   useLLVM = !stdenv.hostPlatform.isDarwin;
                 };
@@ -142,5 +143,6 @@ import ./default.nix
       "wrapCCWith"
       "overrideCC"
       "fetchpatch"
+      "pkgsHostTarget"
     ]
   )

pkgs/development/compilers/rust/rustc.nix

@@ -172,7 +172,7 @@ in stdenv.mkDerivation (finalAttrs: {
   ] ++ optionals (stdenv.hostPlatform.isDarwin && stdenv.hostPlatform.isx86_64) [
     # https://github.com/rust-lang/rust/issues/92173
     "--set rust.jemalloc"
-  ] ++ optionals useLLVM [
+  ] ++ optionals (useLLVM && !stdenv.targetPlatform.isFreeBSD) [
     # https://github.com/NixOS/nixpkgs/issues/311930
     "--llvm-libunwind=${if withBundledLLVM then "in-tree" else "system"}"
     "--enable-use-libcxx"
@@ -262,7 +262,7 @@ in stdenv.mkDerivation (finalAttrs: {
   buildInputs = [ openssl ]
     ++ optionals stdenv.hostPlatform.isDarwin [ libiconv Security zlib ]
     ++ optional (!withBundledLLVM) llvmShared.lib
-    ++ optional (useLLVM && !withBundledLLVM) [
+    ++ optional (useLLVM && !withBundledLLVM && !stdenv.targetPlatform.isFreeBSD) [
       llvmPackages.libunwind
       # Hack which is used upstream https://github.com/gentoo/gentoo/blob/master/dev-lang/rust/rust-1.78.0.ebuild#L284
       (runCommandLocal "libunwind-libgcc" {} ''