Move make_clang_dir handling later so --print-revision works

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 contextlib
@@ skipping 695 matching lines @@
   parser.add_argument('--without-patches', action='store_false',
                       help="don't apply patches (default)", dest='with_patches',
                       default=True)
 
   # For now, these flags are only used for the non-Windows flow, but argparser
   # gets mad if it sees a flag it doesn't recognize.
   parser.add_argument('--no-stdin-hack', action='store_true')
 
   args = parser.parse_args()
 
-  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
   if args.if_needed:
     is_clang_required = False
     # 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):
       is_clang_required = True
     if not is_clang_required:
       return 0
 
   global LLVM_WIN_REVISION, PACKAGE_VERSION
   if args.print_revision:
     if use_head_revision:
       print GetSvnRevision(LLVM_DIR)
     else:
       print PACKAGE_VERSION
     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
+
   # Don't buffer stdout, so that print statements are immediately flushed.
   # Do this only after --print-revision has been handled, else we'll get
   # an error message when this script is run from gn for some reason.
   sys.stdout = os.fdopen(sys.stdout.fileno(), 'w', 0)
 
   if use_head_revision:
     # Use a real revision number rather than HEAD to make sure that the stamp
     # file logic works.
     LLVM_WIN_REVISION = GetSvnRevision(LLVM_REPO_URL)
     PACKAGE_VERSION = LLVM_WIN_REVISION + '-0'
 
     args.force_local_build = True
     # Skip local patches when using HEAD: they probably don't apply anymore.
     args.with_patches = False
 
   return UpdateClang(args)
 
 
 if __name__ == '__main__':
   sys.exit(main())