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:   ++ stdenv.lib.optional (!bootstrapVersion && stdenv.hostPlatform.isDarwin) [
      # https://github.com/NixOS/nixpkgs/issues/57120
      # https://github.com/NixOS/nixpkgs/pull/59197#issuecomment-481972515
      llvm_5
    ]
  
    ++ stdenv.lib.optional (!bootstrapVersion && !stdenv.hostPlatform.isDarwin) [
  