[NaCl SDK] Add keyboard interrupt handlers for python scripts

native_client_sdk/src/build_tools/sdk_tools/sdk_update.py

 #!/usr/bin/env python
 # Copyright (c) 2012 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.
 
 """Shim script for the SDK updater, to allow automatic updating.
 
 The purpose of this script is to be a shim which automatically updates
 sdk_tools (the bundle containing the updater scripts) whenever this script is
 run.
@@ skipping 94 matching lines @@
   args = sys.argv[1:]
   if UpdateSDKTools(args) and RenameSdkToolsDirectory():
     # Call the shell script, just in case this script was updated in the next
     # version of sdk_tools
     return subprocess.call([NACLSDK_SHELL_SCRIPT] + args)
   else:
     return subprocess.call(MakeSdkUpdateMainCmd(args))
 
 
 if __name__ == '__main__':
-  sys.exit(main())
+  try:
+    sys.exit(main())
+  except KeyboardInterrupt:
+    sys.exit(1)