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

build/config/compiler/BUILD.gn

 # Copyright (c) 2013 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.
 
 import("//build/config/android/config.gni")
 import("//build/config/chrome_build.gni")
 import("//build/config/compiler/compiler.gni")
 import("//build/config/nacl/config.gni")
 import("//build/toolchain/ccache.gni")
 
@@ skipping 928 matching lines @@
     defines += [
       "_CRT_NONSTDC_NO_WARNINGS",
       "_CRT_NONSTDC_NO_DEPRECATE",
     ]
   } else if (is_clang && !is_nacl) {
     # TODO(thakis): Remove !is_nacl once
     # https://codereview.webrtc.org/1552863002/ made its way into chromium.
     cflags += [ "-Wall" ]
   }
 
-  if (is_linux) {
-    # 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.
-    cflags += [ "-Wno-unused-result" ]
-  }
-
   if (is_clang) {
     cflags += [
       # Lots of third-party libraries have unused variables. Instead of
       # suppressing them individually, we just blanket suppress them here.
       "-Wno-unused-variable",
     ]
   }
 
   if (is_linux || is_android) {
     cflags += [
@@ skipping 340 matching lines @@
   if (symbol_level == 0) {
     configs = [ ":no_symbols" ]
   } else if (symbol_level == 1) {
     configs = [ ":minimal_symbols" ]
   } else if (symbol_level == 2) {
     configs = [ ":symbols" ]
   } else {
     assert(false)
   }
 }