Build the Clang plugin on Windows.

tools/clang/scripts/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.
 
 """Windows can't run .sh files, so this is a Python implementation of
 update.sh. This script should replace update.sh on all platforms eventually."""
 
 import argparse
 import os
@@ skipping 296 matching lines @@
   if not re.search(r'\b(clang|asan)=1', os.environ.get('GYP_DEFINES', '')):
     print 'Skipping Clang update (clang=1 was not set in GYP_DEFINES).'
     return 0
 
   if re.search(r'\b(make_clang_dir)=', os.environ.get('GYP_DEFINES', '')):
     print 'Skipping Clang update (make_clang_dir= was set in GYP_DEFINES).'
     return 0
 
   parser = argparse.ArgumentParser(description='Build Clang.')
   parser.add_argument('--no-clobber', dest='clobber', action='store_false')
-  parser.add_argument('--tools', nargs='*')
+  parser.add_argument('--tools', nargs='*', default=['plugins'])
   # For now, this flag is only used for the non-Windows flow, but argparser gets
   # mad if it sees a flag it doesn't recognize.
   parser.add_argument('--if-needed', action='store_true')
   return UpdateClang(parser.parse_args())
 
 
 if __name__ == '__main__':
   sys.exit(main())