anchor.diff:      paths = envPaths;
       pathsToLink = [ "/lib" ];
   
  -    postBuild = ''
  -      ${ruby}/bin/ruby ${./gen-bin-stubs.rb} \
  -        "${ruby}/bin/ruby" \
  -        "${confFiles}/Gemfile" \
  -        "$out/${ruby.gemPath}" \
  -        "${bundler}/${ruby.gemPath}" \
  -        ${lib.escapeShellArg binPaths} \
  -        ${lib.escapeShellArg groups}
  -    '' + lib.optionalString (postBuild != null) postBuild;
  +    postBuild = (genStubs binPaths) + lib.optionalString (postBuild != null) postBuild;
   
       meta = { platforms = ruby.meta.platforms; } // meta;
   
  
positive.code: , gemfile ? null
  , lockfile ? null
  , gemset ? null
  , ruby ? defs.ruby
  , gemConfig ? defaultGemConfig
  , postBuild ? null
  
negative.code:           require 'bundler/setup'
          '';
          in stdenv.mkDerivation {
            name = "${drvName}-interactive-environment";
            nativeBuildInputs = [ wrappedRuby bundlerEnv ];
            shellHook = ''
              export OLD_IRBRC="$IRBRC"
  