Get clang updates to work with VS 2017

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 346 matching lines @@
   # Try using the toolchain in depot_tools.
   # This sets environment variables used by SelectVisualStudioVersion below.
   sys.path.append(os.path.join(CHROMIUM_DIR, 'build'))
   import vs_toolchain
   vs_toolchain.SetEnvironmentAndGetRuntimeDllDirs()
 
   # Use gyp to find the MSVS installation, either in depot_tools as per above,
   # or a system-wide installation otherwise.
   sys.path.append(os.path.join(CHROMIUM_DIR, 'tools', 'gyp', 'pylib'))
   import gyp.MSVSVersion
+  #if 'GYP_MSVS_OVERRIDE_PATH' in os.environ:
+  #  return gyp.MSVSVersion.VisualStudioVersion('2017',
+  #                             'Visual Studio 2017',
+  #                             solution_version='12.00',
+  #                             project_version='15.0',
+  #                             flat_sln=False,
+  #                             uses_vcxproj=True,
+  #                             path=os.environ['GYP_MSVS_OVERRIDE_PATH'],
+  #                             sdk_based=False,
+  #                             default_toolset='v141')
   vs_version = gyp.MSVSVersion.SelectVisualStudioVersion(
       vs_toolchain.GetVisualStudioVersion())
   return vs_version
 
 
 def CopyDiaDllTo(target_dir):
   # This script always wants to use the 64-bit msdia*.dll.
   dia_path = os.path.join(GetVSVersion().Path(), 'DIA SDK', 'bin', 'amd64')
   dia_dll = os.path.join(dia_path, DIA_DLL[GetVSVersion().ShortName()])
   CopyFile(dia_dll, target_dir)
@@ skipping 531 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())