anchor.diff:      license = licenses.free;
       homepage = "https://cloud.google.com/sdk/";
       maintainers = with maintainers; [stephenmw zimbatm];
  -    platforms = platforms.linux;
  +    platforms = with platforms; linux ++ darwin;
     };
   }
  
positive.code: with python27Packages;
  
  # other systems not supported yet
  assert stdenv.system == "i686-linux" || stdenv.system == "x86_64-linux";
  
  stdenv.mkDerivation rec {
    name = "google-cloud-sdk-${version}";
  
negative.code:       fetchurl {
          url = "https://dl.google.com/dl/cloudsdk/channels/rapid/downloads/${name}-linux-x86.tar.gz";
          sha256 = "1z2v4bg743qkdlmyyy0z2j5s0g10vbc1643gxrhyz491sk6sp616";
        }
      else if stdenv.system == "x86_64-darwin" then
        fetchurl {
          url = "https://dl.google.com/dl/cloudsdk/channels/rapid/downloads/${name}-darwin-x86_64.tar.gz";
          sha256 = "efbe2074da5a544c09b6bf87a8ca045dc429ac38dfcd5380561987769491d5ba";
        }
      else
        fetchurl {
  