Refactor fileutils.cc/h and fileutils_unittests.cc into their own targets.

webrtc/build/webrtc.gni

 # Copyright (c) 2014 The WebRTC project authors. All Rights Reserved.
 #
 # Use of this source code is governed by a BSD-style license
 # that can be found in the LICENSE file in the root of the source
 # tree. An additional intellectual property rights grant can be found
 # in the file PATENTS.  All contributing project authors may
 # be found in the AUTHORS file in the root of the source tree.
 
 import("//build/config/arm.gni")
 import("//build/config/features.gni")
 import("//build/config/mips.gni")
 import("//build/config/sanitizers/sanitizers.gni")
 import("//build_overrides/build.gni")
 import("//testing/test.gni")
 
 declare_args() {
+  # When set to false, we could replace this with a downstream-specific
+  # implementation
+  rtc_use_default_fileutils = true
+
   # Disable this to avoid building the Opus audio codec.
   rtc_include_opus = true
 
   # Enable this to let the Opus audio codec change complexity on the fly.
   rtc_opus_variable_complexity = false
 
   # Disable to use absolute header paths for some libraries.
   rtc_relative_path = true
 
   # Used to specify an external Jsoncpp include path when not compiling the
@@ skipping 283 matching lines @@
                            ])
     configs += invoker.configs
     configs -= rtc_remove_configs
     configs -= invoker.suppressed_configs
     public_configs = [ rtc_common_inherited_config ]
     if (defined(invoker.public_configs)) {
       public_configs += invoker.public_configs
     }
   }
 }