A fix for annoying clang error "unused-const-variabl" in third_party code.

gyp/libwebp.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': {
     'use_system_libwebp%': 0,
   },
   'conditions': [
     ['use_system_libwebp==0', {
       'targets': [
         {
           'target_name': 'libwebp_dec',
           'type': 'static_library',
           'include_dirs': [
               '../third_party/externals/libwebp',
           ],
+          'cflags!': [ '-Wno-unused-const-variable', ],

[mtklein, 2013/10/28 19:37:37]

Try removing the "!"?  That means "remove this", doesn't it?

[tfarina, 2013/10/28 19:49:11]

I tried both ways, with and without. It doesn't work either.
That is frustrating! I uploaded the version without "!" in patch set 3. PTAL.

           'sources': [
             '../third_party/externals/libwebp/src/dec/alpha.c',
             '../third_party/externals/libwebp/src/dec/buffer.c',
             '../third_party/externals/libwebp/src/dec/frame.c',
             '../third_party/externals/libwebp/src/dec/idec.c',
             '../third_party/externals/libwebp/src/dec/io.c',
             '../third_party/externals/libwebp/src/dec/layer.c',
             '../third_party/externals/libwebp/src/dec/quant.c',
             '../third_party/externals/libwebp/src/dec/tree.c',
             '../third_party/externals/libwebp/src/dec/vp8.c',
@@ skipping 139 matching lines @@
           'link_settings': {
             'libraries': [
               '-lwebp',
             ],
           },
         }
       ],
     }],
   ],
 }