(Temporarily?) disable building JS targets on mac hosts

mojo/public/tools/download_network_service.py

 #!/usr/bin/env python
 # Copyright 2015 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import argparse
 import os
 import sys
 import tempfile
 import zipfile
 
 _PLATFORMS = ["linux-x64", "android-arm"]
 _APPS = ["network_service", "network_service_apptests"]
 _CURRENT_PATH = os.path.dirname(os.path.realpath(__file__))
 sys.path.insert(0, os.path.join(_CURRENT_PATH, "pylib"))
 import gs
 
-if not sys.platform.startswith("linux"):
-  print "Not supported for your platform"
-  sys.exit(0)
-
 script_dir = os.path.dirname(os.path.realpath(__file__))
 
 
 def download_app(app, version, tools_directory):
   prebuilt_directory = os.path.join(script_dir, "prebuilt/%s" % app)
   stamp_path = os.path.join(prebuilt_directory, "VERSION")
 
   try:
     with open(stamp_path) as stamp_file:
       current_version = stamp_file.read().strip()
@@ skipping 48 matching lines @@
     version = version_file.read().strip()
 
   for app in _APPS:
     download_app(app, version, args.tools_directory)
 
   return 0
 
 
 if __name__ == "__main__":
   sys.exit(main())