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

third_party/mesa/mesa.gyp

 # 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.
 
 {
   'variables': {
     'generated_src_dir': 'src/chromium_gensrc',
   },
   'target_defaults': {
     'defines': [
@@ skipping 632 matching lines @@
           # since Android's math library doesn't have sincos().
           # Either -fno-builtin-sin or -fno-builtin-cos works.
           'cflags': [
             '-fno-builtin-sin',
           ],
         }],
         ['OS=="win"', {
           'defines': [
             # Because we're building as a static library
             '_GLAPI_NO_EXPORTS',
+            # Generated files use const only if __cplusplus or __STDC__ is
+            # defined. On Windows, neither is defined, so define YY_USE_CONST
+            # to explicitly enable const.
+            'YY_USE_CONST',
           ],
         }],
       ],
     },
     # Building this target will hide the native OpenGL shared library and
     # replace it with a slow software renderer.
     {
       'target_name': 'osmesa',
       'type': 'loadable_module',
       'mac_bundle': 0,
@@ skipping 72 matching lines @@
                 '<(PRODUCT_DIR)/libosmesa.so',
                 '<(SHARED_LIB_DIR)/libosmesa.so',
               ],
             },
           ],
         },
       ],
     }],
   ],
 }