Add build rules for dart2js.

dart/dart.gyp

Index: dart/dart.gyp
diff --git a/dart/dart.gyp b/dart/dart.gyp
index 844514bc5583edca4afe561cb6ab65fb3e27789a..92f89100f178e2456ae4b39910188d82e063b05c 100644
--- a/dart/dart.gyp
+++ b/dart/dart.gyp
@@ -1,4 +1,4 @@
-# Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
+# 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.
 
@@ -105,6 +105,14 @@
           ],
         },
       ],
-    }
+    },
+    {
+      'target_name': 'dart2js',
+      'type': 'none',
+      'dependencies': [
+        'runtime/dart-runtime.gyp:dart',
+        'utils/compiler/compiler.gyp:dart2js',
+      ],
+    },
   ],
 }