Convert some GN test support targets to static libs.

components/proximity_auth/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("proximity_auth") {
   sources = [
     "authenticator.h",
     "bluetooth_connection.cc",
@@ skipping 75 matching lines @@
   allow_circular_includes_from = [
     "//components/proximity_auth/ble",
     "//components/proximity_auth/cryptauth",
   ]
 
   if (is_chromeos) {
     deps += [ "//chromeos" ]
   }
 }
 
-source_set("test_support") {
+static_library("test_support") {
   testonly = true
 
   sources = [
     "device_to_device_responder_operations.cc",
     "device_to_device_responder_operations.h",
     "fake_connection.cc",
     "fake_connection.h",
     "fake_secure_context.cc",
     "fake_secure_context.h",
     "mock_proximity_auth_client.cc",
@@ skipping 66 matching lines @@
     sources = [
       "run_all_unittests.cc",
     ]
     deps = [
       ":unit_tests",
       "//base",
       "//base/test:test_support",
     ]
   }
 }