Convert some GN test support targets to static libs.

media/base/BUILD.gn

 # Copyright 2014 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.
 
 import("//build/config/android/config.gni")
 import("//build/config/arm.gni")
 import("//build/config/features.gni")
 import("//build/config/ui.gni")
 import("//build/config/linux/pkg_config.gni")
 import("//media/media_options.gni")
@@ skipping 345 matching lines @@
       "yuv_convert.h",
     ]
     configs += [
       "//build/config/compiler:no_size_t_to_int_warning",
       "//media:media_config",
     ]
     all_dependent_configs = [ ":base_for_cast_ios_dependent_config" ]
   }
 }
 
-source_set("test_support") {
+static_library("test_support") {
   testonly = true
   sources = [
     "fake_audio_render_callback.cc",
     "fake_audio_render_callback.h",
     "fake_audio_renderer_sink.cc",
     "fake_audio_renderer_sink.h",
     "fake_demuxer_stream.cc",
     "fake_demuxer_stream.h",
     "fake_media_resources.cc",
     "fake_media_resources.h",
@@ skipping 235 matching lines @@
 
 fuzzer_test("media_container_names_fuzzer") {
   sources = [
     "container_names_fuzzertest.cc",
   ]
   deps = [
     "//base",
     "//media",
   ]
 }