anchor.diff:      "-DCMAKE_BUILD_TYPE=Release"
       "-DCMAKE_CXX_FLAGS=-std=c++11"
     ] ++
  +  # Maybe with compiler-rt this won't be needed?
  +  (stdenv.lib.optional stdenv.isLinux "-DGCC_INSTALL_PREFIX=${gcc}") ++
     (stdenv.lib.optional (stdenv.cc.libc != null) "-DC_INCLUDE_DIRS=${stdenv.cc.libc}/include");
   
     patches = [ ./clang-purity.patch ./clang-exports.patch ];
  
positive.code: 
    enableParallelBuilding = true;
  
    meta = {
      description = "A c, c++, objective-c, and objective-c++ frontend for the llvm compiler";
      homepage    = http://llvm.org/;
  
negative.code: { stdenv, fetch, cmake, libxml2, libedit, llvm, version, clang-tools-extra_src }:
  
  let
    gcc = if stdenv.cc.cc.isGNU or false then stdenv.cc.cc else stdenv.cc.cc.gcc;
  in stdenv.mkDerivation {
    name = "clang-${version}";
  
    unpackPhase = ''
  