anchor.diff: -{ stdenv, fetchFromGitHub, fetchpatch, cmake, bash, gnugrep
  +{ stdenv, fetchFromGitHub, cmake, bash, gnugrep
   , fixDarwinDylibNames
   , file
   , legacySupport ? false
  
positive.code: 
    patches = [
      ./playtests-darwin.patch
      (fetchpatch {
        url = "https://github.com/facebook/zstd/pull/2163.patch";
        sha256 = "07mfjc5f9wy0w2xlj36hyf7g5ax9r2rf6ixhkffhnwc6rwy0q54p";
      })
    ] # This I didn't upstream because if you use posix threads with MinGW it will
      # work fine, and I'm not sure how to write the condition.
      ++ stdenv.lib.optional stdenv.hostPlatform.isWindows ./mcfgthreads-no-pthread.patch;
  
negative.code: 
  stdenv.mkDerivation rec {
    pname = "zstd";
    version = "1.4.8";
  
    src = fetchFromGitHub {
      owner = "facebook";
      repo = "zstd";
      rev = "v${version}";
      sha256 = "018zgigp5xlrb4mgshgrvns0cfbhhcg89cifbjj4rv6s3n9riphw";
    };
  
    nativeBuildInputs = [ cmake ]
  