llvmPackages.{clang,mlir}: Mark big-parallel (#401669)

pkgs/development/compilers/llvm/common/clang/default.nix

@@ -298,6 +298,7 @@ stdenv.mkDerivation (
         ++ (finalAttrs.passthru.hardeningUnsupportedFlags or [ ]);
     };
 
+    requiredSystemFeatures = [ "big-parallel" ];
     meta = llvm_meta // {
       homepage = "https://clang.llvm.org/";
       description = "C language family frontend for LLVM";

pkgs/development/compilers/llvm/common/mlir/default.nix

@@ -87,6 +87,7 @@ stdenv.mkDerivation (finalAttrs: {
     "dev"
   ];
 
+  requiredSystemFeatures = [ "big-parallel" ];
   meta = llvm_meta // {
     # Very broken since the dependencies aren't propagating at all with tblgen through the CMake.
     broken = lib.versionAtLeast release_version "20";