Merge #122044: compiler-rt: Fix build by passing resource dir

Fast-forwarded from staging to staging-next.  See:
https://github.com/NixOS/nixpkgs/pull/111487#issuecomment-840088733

pkgs/development/compilers/llvm/8/default.nix

@@ -18,13 +18,15 @@ let
 
   tools = lib.makeExtensible (tools: let
     callPackage = newScope (tools // { inherit stdenv cmake libxml2 python3 isl release_version version fetch buildLlvmTools; });
-    mkExtraBuildCommands = cc: ''
+    mkExtraBuildCommands0 = cc: ''
       rsrc="$out/resource-root"
       mkdir "$rsrc"
       ln -s "${cc.lib}/lib/clang/${release_version}/include" "$rsrc"
-      ln -s "${targetLlvmLibraries.compiler-rt.out}/lib" "$rsrc/lib"
       echo "-resource-dir=$rsrc" >> $out/nix-support/cc-cflags
     '';
+    mkExtraBuildCommands = cc: mkExtraBuildCommands0 cc + ''
+      ln -s "${targetLlvmLibraries.compiler-rt.out}/lib" "$rsrc/lib"
+    '';
 
   in {
 
@@ -150,7 +152,7 @@ let
       '' + mkExtraBuildCommands cc;
     };
 
-    lldClangNoCompilerRt = wrapCCWith {
+    lldClangNoCompilerRt = wrapCCWith rec {
       cc = tools.clang-unwrapped;
       libcxx = null;
       bintools = wrapBintoolsWith {
@@ -160,7 +162,7 @@ let
       extraPackages = [ ];
       extraBuildCommands = ''
         echo "-nostartfiles" >> $out/nix-support/cc-cflags
-      '';
+      '' + mkExtraBuildCommands0 cc;
     };
 
   });