anchor.diff:  
       // In a precompiled snapshot, the instruction buffer contains script
       // content equivalents
  -    final int result = await createSnapshot(
  +    final int result = await _createSnapshot(
         mainPath: mainPath,
         snapshotPath: snapshotPath,
         depfilePath: depfilePath,
  
positive.code:     '--vm_snapshot_data=$vmSnapshotData',
      '--isolate_snapshot_data=$isolateSnapshotData',
      '--packages=$packages',
      '--script_snapshot=$snapshotPath'
    ];
    if (depfilePath != null) {
      args.add('--dependencies=$depfilePath');
      fs.file(depfilePath).parent.childFile('gen_snapshot.d').writeAsString('$depfilePath: $snapshotterPath\n');
    }
    args.add(mainPath);
    return runCommandAndStreamOutput(args);
  }
  
  
negative.code: const String _kSnapshotKey = 'snapshot_blob.bin';
  const String _kDylibKey = 'libapp.so';
  
  Future<int> _createSnapshot({
    @required String mainPath,
    @required String snapshotPath,
    @required String depfilePath,
    @required String packages
  }) {
    assert(mainPath != null);
    assert(snapshotPath != null);
    assert(depfilePath != null);
    assert(packages != null);
    final String snapshotterPath = artifacts.getArtifactPath(Artifact.genSnapshot, null, BuildMode.debug);
    final String vmSnapshotData = artifacts.getArtifactPath(Artifact.vmSnapshotData);
  