libxml.gyp: remove clang-on-windows specific option

third_party/libxml/libxml.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': {
     'conditions': [
       # Define an "os_include" variable that points at the OS-specific generated
       # headers.  These were generated by running the configure script offline.
       ['os_posix == 1 and OS != "mac" and OS != "ios"', {
@@ skipping 230 matching lines @@
             ['OS=="win"', {
               'product_name': 'libxml2',
               # Disable unimportant 'unused variable' warning, and
               # signed/unsigned comparison warning. The signed/unsigned (4101)
               # is fixed upstream and can be removed eventually.
               # TODO(jschuh): http://crbug.com/167187 size_t -> int
               'msvs_disabled_warnings': [ 4018, 4101, 4267 ],
             }, {  # else: OS!="win"
               'product_name': 'xml2',
             }],
-            ['clang==1', {
-              'msvs_settings': {
-                'VCCLCompilerTool': {
-                  'AdditionalOptions': [
-                    # VS2012's standard lib doesn't provide nan().
-                    '/U__STDC_VERSION__',
-                  ],
-                },
-              },
-            }],
           ],
         }],
       ],
     },
   ],
 }