anchor.diff:  
     # The ultimate test: bootstrap a whole stdenv from the tools specified above and get a package set out of it
     test-pkgs = let
  -    stdenv = import ./. { inherit system bootstrapFiles; };
  -  in import ../../.. {
  +    stdenv = import "${test-pkgspath}/pkgs/stdenv/darwin" { inherit system bootstrapFiles; };
  +  in import test-pkgspath {
       inherit system;
       bootStdenv = stdenv.stdenvDarwin;
     };
  
positive.code: 
        cp -rL ${llvmPackages.clang-unwrapped}/lib/clang $out/lib
  
        cp -d ${libcxx}/lib/libc++*.dylib $out/lib
        cp -d ${libcxxabi}/lib/libc++abi*.dylib $out/lib
  
        mkdir $out/include
        cp -rd ${libcxx}/include/c++     $out/include
  
        cp -d ${icu.out}/lib/libicu*.dylib $out/lib
        cp -d ${zlib.out}/lib/libz.*       $out/lib
  
negative.code: { pkgspath ? ../../.., test-pkgspath ? pkgspath }:
  
  with import pkgspath { system = builtins.currentSystem; };
  
  let
    llvmPackages = llvmPackages_38;
  in rec {
    coreutils_ = coreutils.override (args: {
      # We want coreutils without ACL support.
      aclSupport = false;
  