Adjust pnacl-translate sbtc flag override mechanism to append.

pnacl/driver/tests/driver_tests.py

 #!/usr/bin/python
 # Copyright (c) 2012 The Native Client Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 """Run all python tests in this directory."""
 
 import os
 import sys
 import unittest
 
 MODULES = [
     'expand_response_file_test',
     'help_message_test',
     'strip_test',
+    'translate_options_test',
 ]
 
 # The tested modules live in the parent directory. Set up the import path
 # accordingly.
 my_dir = os.path.dirname(sys.argv[0])
 sys.path.append(os.path.join(my_dir, '..'))
 
 suite = unittest.TestLoader().loadTestsFromNames(MODULES)
 result = unittest.TextTestRunner(verbosity=2).run(suite)
 if result.wasSuccessful():
   sys.exit(0)
 else:
   sys.exit(1)