anchor.diff:      argParser.addFlag('mojo-release', negatable: false, help: 'Use Release build of mojo (default)');
   
       argParser.addOption('app', defaultsTo: 'app.flx');
  -    argParser.addOption('mojo-path', help: 'Path to directory containing mojo_shell and services');
  +    argParser.addOption('mojo-path', help: 'Path to directory containing mojo_shell and services. This is required for a Linux build.');
  +    argParser.addOption('devtools-path', help: 'Path to the mojo_run script in mojo devtools. This is required for an Android build.');
     }
   
     // TODO(abarth): Why not use path.absolute?
  
positive.code:     return file.absolute.path;
    }
  
    Future<int> _runAndroid(String mojoPath, _MojoConfig mojoConfig, String appPath, List<String> additionalArgs) {
      String skyViewerUrl = ArtifactStore.googleStorageUrl('viewer', 'android-arm');
      String command = _makePathAbsolute(path.join(mojoPath, 'mojo', 'devtools', 'common', 'mojo_run'));
      String appName = path.basename(appPath);
      String appDir = path.dirname(appPath);
      String buildFlag = mojoConfig == _MojoConfig.Debug ? '--debug' : '--release';
  
negative.code: 
    @override
    Future<int> run() async {
      if (argResults['mojo-path'] == null && !argResults['android']) {
        _logging.severe('Must specify --mojo-path for Linux.');
        return 1;
      }
  
      if (argResults['devtools-path'] == null && argResults['android']) {
        _logging.severe('Must specify --devtools-path for Android.');
        return 1;
      }
      if (argResults['mojo-debug'] && argResults['mojo-release']) {
  