anchor.diff:      esac
       shift
   done
  +
   if ! [[ -z "$@" ]]; then
      exec "$@"
   fi
  
positive.code: 
    toolchainName = "com.apple.dt.toolchain.XcodeDefault";
    sdkName = "${xcodePlatform}${sdkVer}";
  
    # TODO: expose MACOSX_DEPLOYMENT_TARGET in nix so we can use it here.
    sdkBuildVersion = "17E189";
  
negative.code: { lib, stdenv, makeWrapper, writeText, writeShellScriptBin, runCommand
  , CoreServices, ImageIO, CoreGraphics
  , runtimeShell, callPackage
  , xcodePlatform ? stdenv.targetPlatform.xcodePlatform or "MacOSX"
  