Convert some GN test support targets to static libs.

mojo/edk/test/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("//testing/test.gni")
 
-source_set("test_support") {
+static_library("test_support") {
   testonly = true
   sources = [
     "mojo_test_base.cc",
     "mojo_test_base.h",
     "scoped_ipc_support.cc",
     "scoped_ipc_support.h",
     "test_utils.h",
     "test_utils_posix.cc",
     "test_utils_win.cc",
   ]
@@ skipping 48 matching lines @@
 
   sources = [
     "run_all_perftests.cc",
   ]
 
   if (is_linux && !is_component_build) {
     public_configs = [ "//build/config/gcc:rpath_for_built_shared_libraries" ]
   }
 }
 
-source_set("test_support_impl") {
+static_library("test_support_impl") {
   testonly = true
   deps = [
     "//base",
     "//base/test:test_support",
     "//mojo/public/c/test_support",
     "//mojo/public/cpp/system",
   ]
 
   sources = [
     "test_support_impl.cc",
@@ skipping 37 matching lines @@
     "//mojo/public/c/system/tests:perftests",
   ]
 }
 
 test("mojo_public_system_unittests") {
   deps = [
     ":run_all_unittests",
     "//mojo/public/cpp/system/tests",
   ]
 }