Convert some GN test support targets to static libs.

components/policy/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/chrome_build.gni")
 import("//build/config/features.gni")
 import("//components/policy/resources/policy_templates.gni")
 import("//third_party/protobuf/proto_library.gni")
 import("//tools/grit/grit_rule.gni")
 
@@ skipping 211 matching lines @@
     ]
   }
 
   group("test_support") {
     public_deps = [
       ":chrome_settings_proto_generated_compile",
       ":policy_component",
     ]
   }
 
-  source_set("policy_component_test_support") {
+  static_library("policy_component_test_support") {
     testonly = true
     sources = [
       "core/browser/configuration_policy_pref_store_test.cc",
       "core/browser/configuration_policy_pref_store_test.h",
       "core/common/cloud/mock_cloud_external_data_manager.cc",
       "core/common/cloud/mock_cloud_external_data_manager.h",
       "core/common/cloud/mock_cloud_policy_client.cc",
       "core/common/cloud/mock_cloud_policy_client.h",
       "core/common/cloud/mock_cloud_policy_store.cc",
       "core/common/cloud/mock_cloud_policy_store.h",
@@ skipping 173 matching lines @@
                "--grit_info",
                rebase_path(grit_info_script, root_build_dir),
              ] + grit_defines
       deps = [
         ":add_version",
         ":policy_templates",
       ]
     }
   }
 }