GN: Change rtc_source_set targets --> rtc_static_library

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")
   import("//build/config/android/rules.gni")
 }
 import("../build/webrtc.gni")
 
-rtc_source_set("system_wrappers") {
+rtc_static_library("system_wrappers") {
   sources = [
     "include/aligned_array.h",
     "include/aligned_malloc.h",
     "include/atomic32.h",
     "include/clock.h",
     "include/cpu_features_wrapper.h",
     "include/cpu_info.h",
     "include/critical_section_wrapper.h",
     "include/data_log.h",
     "include/data_log_c.h",
@@ skipping 103 matching lines @@
   }
 
   if (is_win && is_clang) {
     # Suppress warnings from the Chromium Clang plugin (bugs.webrtc.org/163).
     suppressed_configs += [ "//build/config/clang:find_bad_constructs" ]
   }
 
   deps += [ "../base:rtc_base_approved" ]
 }
 
-rtc_source_set("field_trial_default") {
+rtc_static_library("field_trial_default") {
   sources = [
     "include/field_trial_default.h",
     "source/field_trial_default.cc",
   ]
 }
 
-rtc_source_set("metrics_default") {
+rtc_static_library("metrics_default") {
   sources = [
     "include/metrics_default.h",
     "source/metrics_default.cc",
   ]
 }
 
-rtc_source_set("system_wrappers_default") {
+group("system_wrappers_default") {
   deps = [
     ":field_trial_default",
     ":metrics_default",
     ":system_wrappers",
   ]
 }
 
 if (is_android) {
-  rtc_source_set("cpu_features_android") {
+  rtc_static_library("cpu_features_android") {
     sources = [
       "source/cpu_features_android.c",
     ]
 
     deps = [
       "//third_party/android_tools:cpu_features",
     ]
   }
 }
 
 if (is_linux) {
-  rtc_source_set("cpu_features_linux") {
+  rtc_static_library("cpu_features_linux") {
     sources = [
       "source/cpu_features_linux.c",
     ]
   }
 }
 
 if (rtc_include_tests) {
   rtc_test("system_wrappers_unittests") {
     testonly = true
     sources = [
@@ skipping 36 matching lines @@
       "//testing/gtest",
     ]
 
     if (is_android) {
       deps += [ "//testing/android/native_test:native_test_support" ]
 
       shard_timeout = 900
     }
   }
 }