Fix iOS GN build and cleanup system_wrappers

webrtc/modules/utility/BUILD.gn

 # 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/webrtc.gni")
 
 source_set("utility") {
   sources = [
     "include/audio_frame_operations.h",
     "include/file_player.h",
     "include/file_recorder.h",
     "include/helpers_android.h",
     "include/jvm_android.h",
     "include/process_thread.h",
     "source/audio_frame_operations.cc",
     "source/coder.cc",
     "source/coder.h",
     "source/file_player_impl.cc",
     "source/file_player_impl.h",
     "source/file_recorder_impl.cc",
     "source/file_recorder_impl.h",
     "source/helpers_android.cc",
+    "source/helpers_ios.mm",
     "source/jvm_android.cc",
     "source/process_thread_impl.cc",
     "source/process_thread_impl.h",
   ]
 
   configs += [ "../..:common_config" ]
   public_configs = [ "../..:common_inherited_config" ]
 
   if (is_clang) {
     # Suppress warnings from Chrome's Clang plugins.
     # See http://code.google.com/p/webrtc/issues/detail?id=163 for details.
     configs -= [ "//build/config/clang:find_bad_constructs" ]
   }
 
   deps = [
     "../..:webrtc_common",
     "../../common_audio",
     "../../system_wrappers",
     "../audio_coding",
     "../media_file",
   ]
 }