anchor.diff:    # Contains the ruby version heuristics
     rubyVersion = import ./ruby-version.nix { inherit lib; };
   
  +  # Needed during postInstall
  +  buildRuby =
  +    if stdenv.hostPlatform == stdenv.buildPlatform
  +    then "$out/bin/ruby"
  +    else "${buildPackages.ruby}/bin/ruby";
  +
     generic = { version, sha256 }: let
       ver = version;
       tag = ver.gitTag;
  
positive.code:     isRuby25 = ver.majMin == "2.5";
      baseruby = self.override { useRailsExpress = false; };
      self = lib.makeOverridable (
        { stdenv, lib, fetchurl, fetchpatch, fetchFromSavannah, fetchFromGitHub
        , useRailsExpress ? true
        , zlib, zlibSupport ? true
        , openssl, opensslSupport ? true
  
negative.code: { stdenv, buildPackages, lib
  , fetchurl, fetchpatch, fetchFromSavannah, fetchFromGitHub
  , zlib, openssl, gdbm, ncurses, readline, groff, libyaml, libffi, autoreconfHook, bison
  , autoconf, darwin ? null
  , buildEnv, bundler, bundix, Foundation
  