Use checked-in .package file for building and testing

pkg/pkg.gyp

 # 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.
 
 {
   'targets': [
     {
       'target_name': 'pkg_packages',
       'type': 'none',
       'actions': [
         {
           'action_name': 'make_pkg_packages',
           'inputs': [
             '../tools/make_links.py',
             '<!@(["python", "../tools/list_pkg_directories.py", "."])',
             # Exclude DDC's old location in case folks didn't remove it.
             '<!@(["python", "../tools/list_pkg_directories.py", '
                 '"../third_party/pkg", "--exclude=dev_compiler"])',
             '<!@(["python", "../tools/list_pkg_directories.py", '
                 '"../third_party/pkg_tested"])',
             '<!@(["python", "../tools/list_pkg_directories.py", '
                 '"../runtime"])',
             '../sdk/lib/_internal/js_runtime/lib',
             '../sdk/lib/_internal/sdk_library_metadata/lib',
             '../third_party/observatory_pub_packages/packages/charted/lib',
           ],
           'outputs': [
             '<(SHARED_INTERMEDIATE_DIR)/packages.stamp',
+            '<(PRODUCT_DIR)/.packages',
           ],
           'action': [

[Bill Hesse, 2016/09/14 14:30:12]

We will totally remove this, and the tools it calls, in a follow-up CL.  Leaving
it because some buildbots build it explicitly.

-            'python', '../tools/make_links.py',
+            'echo', 'python', '../tools/make_links.py',
             '--timestamp_file=<(SHARED_INTERMEDIATE_DIR)/packages.stamp',
-            '<(PRODUCT_DIR)/packages',
+            '<(PRODUCT_DIR)',
             '<@(_inputs)',
             # Pub imports dart2js as compiler_unsupported so it can work outside
             # the SDK. Map that to the compiler package.
             'compiler/lib:compiler_unsupported'
           ],
         },
       ],
     }
   ],
 }