GN: Use rtc_include_tests variable to exclude tests.

webrtc/system_wrappers/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.
 
 if (is_android) {
   import("//build/config/android/config.gni")
@@ skipping 175 matching lines @@
   source_set("cpu_features_linux") {
     sources = [
       "source/cpu_features_linux.c",
     ]
 
     configs += [ "..:common_config" ]
     public_configs = [ "..:common_inherited_config" ]
   }
 }
 
-# There's no point processing WebRTC standalone tests in a Chromium build.
-if (!build_with_chromium) {
+if (!rtc_include_tests) {
   test("system_wrappers_unittests") {
     testonly = true
     sources = [
       "source/aligned_array_unittest.cc",
       "source/aligned_malloc_unittest.cc",
       "source/clock_unittest.cc",
       "source/condition_variable_unittest.cc",
       "source/critical_section_unittest.cc",
       "source/data_log_c_helpers_unittest.c",
       "source/data_log_c_helpers_unittest.h",
@@ skipping 30 matching lines @@
       ":system_wrappers",
       "../test:test_support_main",
       "//testing/gtest",
     ]
 
     if (is_android) {
       deps += [ "//testing/android/native_test:native_test_support" ]
     }
   }
 }