anchor.diff:      }
       if (useDfe) {
         args.add('--preview-dart-2');
  +    } else {
  +      args.add("--no-preview-dart-2");
       }
       args
         ..addAll(vmOptions)
  
positive.code:     var args = ["--snapshot=$snapshot", "--snapshot-kind=app-jit"];
      if (useDfe) {
        args.add("--preview-dart-2");
      }
      args.addAll(arguments);
  
  
negative.code:         args.add('--no-background-compilation');
        }
      } else {
        args.add('--no-preview-dart-2');
        if (_isStrong) {
          args.add('--strong');
        }
  