Add machine flag to our build.dart

lib/component_build.dart

 // Copyright (c) 2012, 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.
 
 /**
  * Common logic to make it easy to create a `build.dart` for your project.
  *
  * The `build.dart` script is invoked automatically by the Editor whenever a
  * file in the project changes. It must be placed in the root of a project
  * (where pubspec.yaml lives) and should be named exactly 'build.dart'.
@@ skipping 80 matching lines @@
 }
 
 /** Handle --changed, --removed, --clean and --help command-line args. */
 ArgResults _processArgs(List<String> arguments) {
   var parser = new ArgParser()
     ..addOption("changed", help: "the file has changed since the last build",
         allowMultiple: true)
     ..addOption("removed", help: "the file was removed since the last build",
         allowMultiple: true)
     ..addFlag("clean", negatable: false, help: "remove any build artifacts")
+    ..addFlag("machine", negatable: false,
+        help: "produce warnings in a machine parseable format")
     ..addFlag("help", negatable: false, help: "displays this help and exit");
   var args = parser.parse(arguments);
   if (args["help"]) {
     print(parser.getUsage());
     exit(0);
   }
   return args;
 }