anchor.diff:  in
   stdenv.mkDerivation rec {
     name = "gn-${version}";
  -  version = "20181031";
  +  version = "20190726";
   
     src = fetchgit {
       url = "https://gn.googlesource.com/gn";
       inherit rev sha256;
     };
  -
  -  postPatch = ''
  -    # FIXME Needed with old Apple SDKs
  -    substituteInPlace base/mac/foundation_util.mm \
  -      --replace "NSArray<NSString*>*" "NSArray*"
  -  '';
   
     nativeBuildInputs = [ ninja python2 git ];
     buildInputs = lib.optionals stdenv.isDarwin (with darwin; with apple_sdk.frameworks; [
  
positive.code:   ]);
  
    buildPhase = ''
      python build/gen.py --no-sysroot --no-last-commit-position
      ln -s ${lastCommitPosition} out/last_commit_position.h
      ninja -j $NIX_BUILD_CORES -C out gn
    '';
  
negative.code: , git, ninja, python2 }:
  
  let
    rev = "0bc16a82ea001ad9c94b870f097034be5c8e40b4";
    sha256 = "01as6q5xr0smiihm9m1x74pykd2jcqi4rhv8irmv43v2f0pxwzi5";
  
    shortRev = builtins.substring 0 7 rev;
    lastCommitPosition = writeText "last_commit_position.h" ''
  