zig: remove unused LLVM and Clang references from closure (#578101)

pkgs/development/compilers/zig/generic.nix

@@ -7,6 +7,7 @@
   xcbuild,
   libxml2,
   ninja,
+  removeReferencesTo,
   zlib,
   coreutils,
   callPackage,
@@ -35,6 +36,7 @@ stdenv.mkDerivation (finalAttrs: {
     cmake
     (lib.getDev llvmPackages.llvm.dev)
     ninja
+    removeReferencesTo
   ]
   ++ lib.optionals stdenv.hostPlatform.isDarwin [
     # provides xcode-select, which is required for SDK detection
@@ -119,6 +121,19 @@ stdenv.mkDerivation (finalAttrs: {
     install -Dm444 ../zig-out/doc/langref.html -t $doc/share/doc/zig-${finalAttrs.version}/html
   '';
 
+  # Drop unused LLVM/Clang paths left by static linking.
+  postFixup = ''
+    remove-references-to \
+      -t ${lib.getLib llvmPackages.llvm} \
+      -t ${lib.getLib llvmPackages.libclang} \
+      $out/bin/zig
+  '';
+
+  disallowedReferences = [
+    (lib.getLib llvmPackages.llvm)
+    (lib.getLib llvmPackages.libclang)
+  ];
+
   doInstallCheck = true;
   installCheckPhase = ''
     runHook preInstallCheck