Mojo: Only link against one system impl

mojo/mojo_examples.gypi

 # Copyright 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.
 
 {
   'targets': [
     {
       'target_name': 'mojo_echo_client',
       'type': 'loadable_module',
       'dependencies': [
@@ skipping 354 matching lines @@
       'dependencies': [
         '../base/base.gyp:base',
         '../cc/cc.gyp:cc',
         '../cc/cc.gyp:cc_surfaces',
         '../skia/skia.gyp:skia',
         '../ui/gfx/gfx.gyp:gfx',
         '../ui/gfx/gfx.gyp:gfx_geometry',
         'mojo_base.gyp:mojo_application_chromium',
         'mojo_base.gyp:mojo_common_lib',
         'mojo_base.gyp:mojo_environment_chromium',
-        'mojo_base.gyp:mojo_system_impl',
         'mojo_geometry_bindings',
         'mojo_geometry_lib',
         'mojo_native_viewport_bindings',
         'mojo_surfaces_bindings',
         'mojo_surfaces_app_bindings',
         'mojo_surfaces_lib',
         '<(mojo_gles2_for_loadable_module)',
         '<(mojo_system_for_loadable_module)',
       ],
       'sources': [
@@ skipping 34 matching lines @@
       'dependencies': [
         '../base/base.gyp:base',
         '../cc/cc.gyp:cc',
         '../cc/cc.gyp:cc_surfaces',
         '../skia/skia.gyp:skia',
         '../ui/gfx/gfx.gyp:gfx',
         '../ui/gfx/gfx.gyp:gfx_geometry',
         'mojo_base.gyp:mojo_application_chromium',
         'mojo_base.gyp:mojo_common_lib',
         'mojo_base.gyp:mojo_environment_chromium',
-        'mojo_base.gyp:mojo_system_impl',
         'mojo_geometry_bindings',
         'mojo_geometry_lib',
         'mojo_surfaces_app_bindings',
         'mojo_surfaces_bindings',
         'mojo_surfaces_lib',
         '<(mojo_system_for_loadable_module)',
       ],
       'sources': [
         'examples/surfaces_app/child_app.cc',
         'examples/surfaces_app/child_impl.cc',
@@ skipping 404 matching lines @@
           ],
           'sources': [
             'examples/dbus_echo/dbus_echo_app.cc',
             'public/cpp/application/lib/mojo_main_standalone.cc',
           ],
         },
       ],
     }],
   ],
 }