clang/win update.py: Put gnuwin last in path.

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.
 
 """This script is used to download prebuilt clang binaries.
 
 It is also used by package.py to build the prebuilt clang binaries."""
 
 import argparse
@@ skipping 309 matching lines @@
   gnuwin_dir = os.path.join(LLVM_BUILD_TOOLS_DIR, 'gnuwin')
   GNUWIN_VERSION = '1'
   GNUWIN_STAMP = os.path.join(gnuwin_dir, 'stamp')
   if ReadStampFile(GNUWIN_STAMP) == GNUWIN_VERSION:
     print 'GNU Win tools already up to date.'
   else:
     zip_name = 'gnuwin-%s.zip' % GNUWIN_VERSION
     DownloadAndUnpack(CDS_URL + '/tools/' + zip_name, LLVM_BUILD_TOOLS_DIR)
     WriteStampFile(GNUWIN_VERSION, GNUWIN_STAMP)
 
-  os.environ['PATH'] = gnuwin_dir + os.pathsep + os.environ.get('PATH', '')
+  os.environ['PATH'] = os.environ.get('PATH', '') + os.pathsep + gnuwin_dir
 
 
 vs_version = None
 def GetVSVersion():
   global vs_version
   if vs_version:
     return vs_version
 
   # Try using the toolchain in depot_tools.
   # This sets environment variables used by SelectVisualStudioVersion below.
@@ skipping 520 matching lines @@
     args.force_local_build = True
     if 'OS=android' not in os.environ.get('GYP_DEFINES', ''):
       # Only build the Android ASan rt on ToT bots when targetting Android.
       args.with_android = False
 
   return UpdateClang(args)
 
 
 if __name__ == '__main__':
   sys.exit(main())