Disable harmless warnings for 3rdparty code: zlib.

third_party/zlib/zlib.gyp

 # Copyright (c) 2011 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': [
       [ 'os_posix == 1 and OS != "mac" and OS != "openbsd"', {
         # Link to system .so since we already use it due to GTK.
         # TODO(pvalchev): OpenBSD is purposefully left out, as the system
@@ skipping 61 matching lines @@
               ],
             }],
             ['OS=="mac" or os_bsd==1 or OS=="android"', {
               # Mac, Android and the BSDs don't have fopen64, ftello64, or
               # fseeko64. We use fopen, ftell, and fseek instead on these
               # systems.
               'defines': [
                 'USE_FILE32API'
               ],
             }],
+            ['clang==1', {
+              'xcode_settings': {
+                'WARNING_CFLAGS': [
+                  # zlib uses `if ((a == b))` for some reason.
+                  '-Wno-parentheses-equality',
+                ],
+              },
+              'cflags': [
+                '-Wno-parentheses-equality',
+              ],
+            }],
           ],
         },
       ],
     }, {
       'targets': [
         {
           'target_name': 'zlib',
           'type': 'static_library',
           'direct_dependent_settings': {
             'defines': [
@@ skipping 27 matching lines @@
           'link_settings': {
             'libraries': [
               '-lz',
             ],
           },
         },
       ],
     }],
   ],
 }