anchor.diff:  
     preBuild = ''
       sed -i -e 's,C_INCLUDE_PATH,"${stdenv.gcc.libc}/include/",' \
  -      -e 's,CPP_HOST,"${triplet}",' \
  +      -e 's,CPP_HOST,"'$(${stdenv.gcc.gcc}/bin/gcc -dumpmachine)'",' \
         -e 's,CPP_INCLUDE_PATH,"${stdenv.gcc.gcc}/include/c++/${stdenv.gcc.gcc.version}",' \
         tools/clang/lib/Frontend/InitHeaderSearch.cpp
   
  
positive.code:     description = "A C language family frontend for LLVM";
      license = "BSD";
      maintainers = with stdenv.lib.maintainers; [viric shlevy];
      platforms = with stdenv.lib.platforms; linux;
    };
  }
  
negative.code: { stdenv, fetchurl, perl, groff, llvm }:
  
  let version = "2.9"; in
  
  stdenv.mkDerivation {
    name = "clang-${version}";
  