Decoupling rtc_base from apple specific code [without cyclic deps]

webrtc/examples/BUILD.gn

 # Copyright (c) 2016 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("../webrtc.gni")
 if (is_android) {
@@ skipping 421 matching lines @@
         ]
       }
 
       rtc_ios_xctest_test("apprtcmobile_tests") {
         info_plist = "objc/AppRTCMobile/ios/Info.plist"
         sources = [
           "objc/AppRTCMobile/ios/main.m",
         ]
         deps = [
           ":apprtcmobile_test_sources",
+          "../rtc_base:rtc_base_apple",
         ]
         ldflags = [ "-all_load" ]
       }
     }
   }
 }
 
 if (is_linux || is_win) {
   config("peerconnection_client_warnings_config") {
     cflags = []
@@ skipping 211 matching lines @@
       suppressed_configs += [ "//build/config/clang:find_bad_constructs" ]
     }
 
     deps = [
       "../base:rtc_base",
       "../base:rtc_base_approved",
       "../p2p:libstunprober",
       "../p2p:rtc_p2p",
       "../system_wrappers:field_trial_default",
     ]
+
+    if (is_ios || is_mac) {
+      deps += [ "../rtc_base:rtc_base_apple" ]
+    }
   }
 }