anchor.diff: -{ stdenv, fetchgit, cmake }:
  +{ stdenv, fetchgit, cmake
  +, hostPlatform, buildPlatform
  +}:
   
  +let
  +  nativeBuild = hostPlatform == buildPlatform;
  +in
   stdenv.mkDerivation rec {
     name = "microsoft_gsl-${version}";
     version = "2017-02-13";
  
positive.code: 
    meta = with stdenv.lib; {
      description = "Functions and types that are suggested for use by the C++ Core Guidelines";
      homepage = https://github.com/Microsoft/GSL;
      license = licenses.mit;
      platforms = platforms.all;
      maintainers = with maintainers; [ xwvvvvwx ];
    };
  }
  
negative.code:     sha256 = "03d17mnx6n175aakin313308q14wzvaa9pd0m1yfk6ckhha4qf35";
    };
  
  
    # build phase just runs the unit tests, so skip it if
    # we're doing a cross build
    nativeBuildInputs = [ cmake ];
    buildPhase = if nativeBuild then "make" else "true";
  
    installPhase = ''
      mkdir -p $out/include
  