linux/clang: Disable the last two warnings, turn on -Werror

breakpad/breakpad.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.
 
 {
   'includes': [
     'breakpad_sender.gypi',
     'breakpad_handler.gypi',
   ],
   'conditions': [
@@ skipping 595 matching lines @@
             'src/tools/linux/md2core/minidump_memory_range.h',
             'src/tools/linux/md2core/minidump_memory_range_unittest.cc',
           ],
 
           'include_dirs': [
             'linux', # Use our copy of breakpad_googletest_includes.h
             'src',
             '..',
             '.',
           ],
+          'conditions': [
+            [ 'clang == 1', {
+              'cflags': [
+                # See http://crbug.com/138571#c18
+                '-Wno-unused-value',
+              ],
+            }],
+          ],
         },
         {
           'target_name': 'linux_dumper_unittest_helper',
           'type': 'executable',
           'dependencies': [
             'breakpad_processor_support',
           ],
           'sources': [
             'src/client/linux/minidump_writer/linux_dumper_unittest_helper.cc',
           ],
@@ skipping 127 matching lines @@
           'include_dirs': [
             'src',
             'src/client/mac/Framework',
             'src/common/mac',
           ],
         },
       ],
     }],
   ],
 }