clang upload.sh: don't download Clang binaries from clang_upload bots.

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 704 matching lines @@
                       help='select which chrome tools to build',
                       default=['plugins', 'blink_gc_plugin'])
   parser.add_argument('--without-android', action='store_false',
                       help='don\'t build Android ASan runtime (linux only)',
                       dest='with_android',
                       default=sys.platform.startswith('linux'))
   args = parser.parse_args()
 
   if args.if_needed:
     is_clang_required = False
+    # We don't need to download the toolchain on upload bots during runhooks.
+    if 'LLVM_DOWNLOAD_NOT_NEEDED' in os.environ:
+      print ('Skipping downloading Clang toolchain binaries as '
+             'LLVM_DOWNLOAD_NOT_NEEDED is found in the environment')

[hans, 2016/03/04 19:52:28]

can we call it LLVM_FORCE_LOCAL_BUILD instead and tie it in with the
corresponding flag?

+      return 0
     # clang is always used on Mac and Linux.
     if sys.platform == 'darwin' or sys.platform.startswith('linux'):
       is_clang_required = True
     # clang requested via $GYP_DEFINES.
     if re.search(r'\b(clang|asan|lsan|msan|tsan)=1',
                  os.environ.get('GYP_DEFINES', '')):
       is_clang_required = True
     # clang previously downloaded, keep it up-to-date.
     # If you don't want this, delete third_party/llvm-build on your machine.
     if os.path.isdir(LLVM_BUILD_DIR):
@@ skipping 30 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())