gyp: supress more warnings for zlib

gyp/zlib.gyp

 # Copyright 2014 Google Inc.
 #
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 {
   'variables': {
     'skia_warnings_as_errors': 0,
   },
   'targets': [
   {
       'target_name': 'zlib',
       'conditions': [
         [ 'skia_android_framework', {
           'type': 'none',
           'direct_dependent_settings': {
               'include_dirs': [ 'external/zlib' ],
               'link_settings': { 'libraries': [ '-lz' ] },
           },
         }, {
           'type': 'static_library',
           'variables': {
             'skia_zlib_flags' : [
               '-Wno-unused-value',
               '-Wno-shift-negative-value',
+              '-Wno-unknown-warning-option',
             ],
           },
           'cflags': [ '<@(skia_zlib_flags)' ],
           'xcode_settings': { 'WARNING_CFLAGS': [ '<@(skia_zlib_flags)' ], },
           'sources': [
             '../third_party/externals/zlib/adler32.c',
             '../third_party/externals/zlib/compress.c',
             '../third_party/externals/zlib/crc32.c',
             '../third_party/externals/zlib/deflate.c',
             '../third_party/externals/zlib/gzclose.c',
@@ skipping 17 matching lines @@
               '../third_party/externals/zlib',
             ],
           },
           'defines': [
             '_CRT_NONSTDC_NO_DEPRECATE',
           ],
         }],
       ],
   }],
 }