anchor.diff: -{ stdenv, fetchurl, cmake, ninja, llvm, llvm_8, curl, tzdata
  +{ stdenv, fetchurl, cmake, ninja, llvm_5, llvm_8, curl, tzdata
   , python, libconfig, lit, gdb, unzip, darwin, bash
   , callPackage, makeWrapper, targetPackages
   , bootstrapVersion ? false
  
positive.code:   ]
  
    ++ stdenv.lib.optional (bootstrapVersion) [
      libconfig llvm
    ]
  
    ++ stdenv.lib.optional stdenv.hostPlatform.isDarwin (with darwin.apple_sdk.frameworks; [
  
negative.code:   else
      "";
  
    doCheck = !bootstrapVersion;
  
    checkPhase = stdenv.lib.optionalString doCheck ''
      # Build default lib test runners
  