anchor.diff:  
     gccMultiStdenv = overrideCC stdenv gcc_multi;
     clangMultiStdenv = overrideCC stdenv clang_multi;
  +  multiStdenv = if stdenv.cc.isClang then clangMultiStdenv else gccMultiStdenv;
   
     gcc_debug = lowPrio (wrapCC (gcc.cc.override {
       stripped = false;
  
positive.code:   # A stdenv capable of building 32-bit binaries.  On x86_64-linux,
    # it uses GCC compiled with multilib support; on i686-linux, it's
    # just the plain stdenv.
    stdenv_32bit = lowPrio (
      if system == "x86_64-linux" then
        overrideCC stdenv gcc_multi
      else
        stdenv);
  
    stdenvNoCC = stdenv.override { cc = null; };
  
  
negative.code:   };
  
    #Use this instead of stdenv to build with clang
    clangStdenv = if stdenv.cc.isClang then stdenv else lowPrio llvmPackages.stdenv;
    clang-sierraHack-stdenv = overrideCC stdenv clang-sierraHack;
    libcxxStdenv = if stdenv.isDarwin then stdenv else lowPrio llvmPackages.libcxxStdenv;
  
  