linux/gyp: Find missing symbols at build time, not runtime.

ui/wm/wm.gyp

 # 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.
 
 {
   'variables': {
     'chromium_code': 1,
   },
   'targets': [
     {
@@ skipping 80 matching lines @@
         'core/window_modality_controller.cc',
         'core/window_modality_controller.h',
         'core/window_util.cc',
         'core/window_util.h',
         'core/wm_core_switches.cc',
         'core/wm_core_switches.h',
         'core/wm_state.cc',
         'core/wm_state.h',
         'wm_export.h',
       ],
+      'conditions': [
+        ['use_x11==1', {
+          'link_settings': { 'libraries': [ '-lX11' ] },
+        }],
+      ],
     },
     {
       # GN version: //ui/wm:test_support
       'target_name': 'wm_test_support',
       'type': 'static_library',
       'dependencies': [
         '../../skia/skia.gyp:skia',
         '../aura/aura.gyp:aura',
         '../events/events.gyp:events',
         '../events/events.gyp:events_base',
@@ skipping 38 matching lines @@
         'core/transient_window_manager_unittest.cc',
         'core/transient_window_stacking_client_unittest.cc',
         'core/user_activity_detector_unittest.cc',
         'core/visibility_controller_unittest.cc',
         'core/window_animations_unittest.cc',
         'core/window_util_unittest.cc',
       ],
     },
   ],
 }