Linux: Enable ODR violation detection.

third_party/libphonenumber/libphonenumber.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.
 
 {
   'target_defaults': {
     'include_dirs': [
       'src',
       'src/test',
       # The libphonenumber source (and test code) expects the
@@ skipping 122 matching lines @@
       '../../testing/gmock.gyp:gmock',
       '../../testing/gtest.gyp:gtest',
       'libphonenumber_without_metadata',
     ],
     'conditions': [
       ['OS=="win"', {
         'action': [
           '/wo4309',
         ],
       }],
+      # libphonenumber needs to fix their ODR violations. http://crbug.com/456021
+      ['OS=="linux"', {
+        'ldflags!': [
+          '-Wl,--detect-odr-violations',
+        ],
+      }],
     ],
   }]
 }