[infra] Roll clang toolchain forward

tools/buildtools/update.py

 #!/usr/bin/env python
 # Copyright 2017 The Dart project authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 """Pulls down tools required to build Dart."""
 
 import os
 import subprocess
 import shutil
 import sys
 
 THIS_DIR = os.path.abspath(os.path.dirname(__file__))
 DART_ROOT = os.path.abspath(os.path.join(THIS_DIR, '..', '..'))
 BUILDTOOLS = os.path.join(DART_ROOT, 'buildtools')
 TOOLS_BUILDTOOLS = os.path.join(DART_ROOT, 'tools', 'buildtools')
 TOOLCHAIN = os.path.join(BUILDTOOLS, 'toolchain')
 
 sys.path.insert(0, os.path.join(DART_ROOT, 'tools'))
 import find_depot_tools
 
 DEPOT_PATH = find_depot_tools.add_depot_tools_to_path()
 
 
 def Update():
   path = os.path.join(BUILDTOOLS, 'update.sh')
-  command = ['/bin/bash', path, '--toolchain', '--gn']
+  command = ['/bin/bash', path, '--clang', '--gn']
   return subprocess.call(command, cwd=DART_ROOT)
 
 
 def UpdateGNOnWindows():
   sha1_file = os.path.join(BUILDTOOLS, 'win', 'gn.exe.sha1')
   downloader_script = os.path.join(
       DEPOT_PATH, 'download_from_google_storage.py')
   download_cmd = [
     'python',
     downloader_script,
@@ skipping 57 matching lines @@
     if result != 0:
       return result
     return UpdateClangFormatOnWindows()
   if Update() != 0:
     return 1
   return CopyClangFormat()
 
 
 if __name__ == '__main__':
   sys.exit(main(sys.argv))