clang/win: Build chromium code without -Wno-incompatible-pointer-types.

third_party/libxml/BUILD.gn

 # Copyright (c) 2013 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.
 
 # Define an "os_include" variable that points at the OS-specific generated
 # headers.  These were generated by running the configure script offline.
 if (is_linux || is_android || is_nacl) {
   os_include = "linux"
 } else if (is_mac || is_ios) {
   os_include = "mac"
@@ skipping 169 matching lines @@
       # threads.c attempts to forward declare a pthread_equal which doesn't
       # match the prototype in pthreads.h
       "-Wno-ignored-attributes",
     ]
   }
   config("libxml_warnings") {
     if (is_clang) {
       cflags += [
         # libxml casts from int to long to void*.
         "-Wno-int-to-void-pointer-cast",
+
+        # libxml passes a volatile LPCRITICAL_SECTION* to a function expecting
+        # a void* volatile*.
+        "-Wno-incompatible-pointer-types",
       ]
     }
   }
   configs += [ ":libxml_warnings" ]
 
   include_dirs = [ "$os_include" ]
 }