Allow dartanalyzer to parse options after the filename argument.

pkg/analyzer/lib/options.dart

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library options;
 
 import 'dart:io';
 
 import 'package:args/args.dart';
 
@@ skipping 225 matching lines @@
  * options/flags, this class can be replaced with a simple [ArgParser] instance.
  */
 class _CommandLineParser {
 
   final List<String> _knownFlags;
   final ArgParser _parser;
 
   /** Creates a new command line parser */
   _CommandLineParser()
     : _knownFlags = <String>[],
-      _parser = new ArgParser();
+      _parser = new ArgParser(allowTrailingOptions: true);
 
 
   /**
    * Defines a flag.
    *
    * See [ArgParser.addFlag()].
    */
   void addFlag(String name, {String abbr, String help, bool defaultsTo: false,
       bool negatable: true, void callback(bool value), bool hide: false}) {
     _knownFlags.add(name);
@@ skipping 83 matching lines @@
 
   _getNextFlagIndex(args, i) {
     for ( ; i < args.length; ++i) {
       if (args[i].startsWith('--')) {
         return i;
       }
     }
     return i;
   }
 }