linux: Build third-party code with -Wunused-result.

build/common.gypi

 # 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.
 
 # IMPORTANT:
 # Please don't directly include this file if you are building via gyp_chromium,
 # since gyp_chromium is automatically forcing its inclusion.
 {
   # Variables expected to be overriden on the GYP command line (-D) or by
   # ~/.gyp/include.gypi.
@@ skipping 3145 matching lines @@
             # When we don't control the compiler, don't use -Wall for
             # third-party code either.
             'cflags!': [ '-Wall' ],
           }],
           # TODO: Fix all warnings on chromeos too.
           [ 'os_posix==1 and OS!="mac" and OS!="ios" and (clang!=1 or chromeos==1)', {
             'cflags!': [
               '-Werror',
             ],
           }],
-          [ 'os_posix==1 and os_bsd!=1 and OS!="mac" and OS!="android"', {
-            'cflags': [
-              # Don't warn about ignoring the return value from e.g. close().
-              # This is off by default in some gccs but on by default in others.
-              # BSD systems do not support this option, since they are usually
-              # using gcc 4.2.1, which does not have this flag yet.
-              '-Wno-unused-result',
-            ],
-          }],
           [ 'OS=="win"', {
             'defines': [
               '_CRT_SECURE_NO_DEPRECATE',
               '_CRT_NONSTDC_NO_WARNINGS',
               '_CRT_NONSTDC_NO_DEPRECATE',
               '_SCL_SECURE_NO_DEPRECATE',
             ],
             'msvs_disabled_warnings': [
               # forcing value to bool 'true' or 'false' (performance warning)
               4800,
@@ skipping 3238 matching lines @@
     # settings in target dicts.  SYMROOT is a special case, because many other
     # Xcode variables depend on it, including variables such as
     # PROJECT_DERIVED_FILE_DIR.  When a source group corresponding to something
     # like PROJECT_DERIVED_FILE_DIR is added to a project, in order for the
     # files to appear (when present) in the UI as actual files and not red
     # red "missing file" proxies, the correct path to PROJECT_DERIVED_FILE_DIR,
     # and therefore SYMROOT, needs to be set at the project level.
     'SYMROOT': '<(DEPTH)/xcodebuild',
   },
 }