Check for SVN earlier in clang's update.py script

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 432 matching lines @@
 
   if args.with_android and not os.path.exists(ANDROID_NDK_DIR):
     print 'Android NDK not found at ' + ANDROID_NDK_DIR
     print 'The Android NDK is needed to build a Clang whose -fsanitize=address'
     print 'works on Android. See '
     print 'https://www.chromium.org/developers/how-tos/android-build-instructions'
     print 'for how to install the NDK, or pass --without-android.'
     return 1
 
   DownloadHostGcc(args)
-  AddSvnToPathOnWin()
   AddCMakeToPath()
   AddGnuWinToPath()
 
   DeleteChromeToolsShim()
 
   Checkout('LLVM', LLVM_REPO_URL + '/llvm/trunk', LLVM_DIR)
   Checkout('Clang', LLVM_REPO_URL + '/cfe/trunk', CLANG_DIR)
   if sys.platform != 'darwin':
     Checkout('LLD', LLVM_REPO_URL + '/lld/trunk', LLD_DIR)
   elif os.path.exists(LLD_DIR):
@@ skipping 410 matching lines @@
   if args.lto_gold_plugin and not sys.platform.startswith('linux'):
     print '--lto-gold-plugin is only effective on Linux. Ignoring the option.'
     args.lto_gold_plugin = False
 
   if args.if_needed:
     # TODO(thakis): Can probably remove this and --if-needed altogether.
     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
 
+  # Get svn if we're going to use it to check the revision or do a local build.
+  if (use_head_revision or args.llvm_force_head_revision or
+      args.force_local_build):
+    AddSvnToPathOnWin()
+
   global CLANG_REVISION, PACKAGE_VERSION
   if args.print_revision:
     if use_head_revision or args.llvm_force_head_revision:
       print GetSvnRevision(LLVM_DIR)
     else:
       print PACKAGE_VERSION
     return 0
 
   if args.print_clang_version:
     sys.stdout.write(VERSION)
@@ skipping 13 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())