Fix GYP and GN references that are invalid in Chromium builds.

talk/build/merge_ios_libs.gyp

 #
 # libjingle
 # Copyright 2015 Google Inc.
 #
 # Redistribution and use in source and binary forms, with or without
 # modification, are permitted provided that the following conditions are met:
 #
 #  1. Redistributions of source code must retain the above copyright notice,
 #     this list of conditions and the following disclaimer.
 #  2. Redistributions in binary form must reproduce the above copyright notice,
@@ skipping 19 matching lines @@
     ['OS=="ios" or OS=="mac"', {
       'targets': [
         {
           'target_name': 'libjingle_peerconnection_objc_no_op',
           'includes': [ 'objc_app.gypi' ],
           'type': 'executable',
           'dependencies': [
             '<(webrtc_root)/system_wrappers/system_wrappers.gyp:field_trial_default',
             '../libjingle.gyp:libjingle_peerconnection_objc',
           ],
-          'sources': ['<(DEPTH)/webrtc/build/no_op.cc',],
+          'sources': ['<(webrtc_root)/build/no_op.cc',],
         },
       ],
     }]
   ],
 }