Add -fms-compatibility-version=19 to the clang-cl self-host

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 419 matching lines @@
       print 'Invalid --gcc-toolchain: "%s"' % args.gcc_toolchain
       print '"%s" does not appear to be valid.' % cc
       return 1
 
     # Set LD_LIBRARY_PATH to make auxiliary targets (tablegen, bootstrap
     # compiler, etc.) find the .so.
     libstdcpp = subprocess.check_output(
         [cxx, '-print-file-name=libstdc++.so.6']).rstrip()
     os.environ['LD_LIBRARY_PATH'] = os.path.dirname(libstdcpp)
 
-  cflags = cxxflags = ldflags = []
+  cflags = []
+  cxxflags = []
+  ldflags = []
 
   base_cmake_args = ['-GNinja',
                      '-DCMAKE_BUILD_TYPE=Release',
                      '-DLLVM_ENABLE_ASSERTIONS=ON',
                      '-DLLVM_ENABLE_THREADS=OFF',
                      '-DLLVM_ENABLE_TIMESTAMPS=OFF',
                      ]
 
   if args.bootstrap:
     print 'Building bootstrap compiler'
@@ skipping 18 matching lines @@
       # compiler can start.
       CopyFile(libstdcpp, os.path.join(LLVM_BOOTSTRAP_INSTALL_DIR, 'lib'))
 
     if sys.platform == 'win32':
       cc = os.path.join(LLVM_BOOTSTRAP_INSTALL_DIR, 'bin', 'clang-cl.exe')
       cxx = os.path.join(LLVM_BOOTSTRAP_INSTALL_DIR, 'bin', 'clang-cl.exe')
       # CMake has a hard time with backslashes in compiler paths:
       # https://stackoverflow.com/questions/13050827
       cc = cc.replace('\\', '/')
       cxx = cxx.replace('\\', '/')
+      # If we're using VS 2015, tell the stage 1 compiler to act like it.
+      if GetVSVersion().ShortName().startswith('2015'):
+        cflags += ['-fms-compatibility-version=19']
+        cxxflags += ['-fms-compatibility-version=19']
     else:
       cc = os.path.join(LLVM_BOOTSTRAP_INSTALL_DIR, 'bin', 'clang')
       cxx = os.path.join(LLVM_BOOTSTRAP_INSTALL_DIR, 'bin', 'clang++')
 
     if args.gcc_toolchain:
       # Tell the bootstrap compiler to use a specific gcc prefix to search
       # for standard library headers and shared object files.
       cflags = ['--gcc-toolchain=' + args.gcc_toolchain]
       cxxflags = ['--gcc-toolchain=' + args.gcc_toolchain]
     print 'Building final compiler'
@@ skipping 298 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())