Convert some component source sets to static library

components/search/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.
 
-source_set("search") {
+static_library("search") {
   sources = [
     "search.cc",
     "search.h",
     "search_switches.cc",
     "search_switches.h",
   ]
 
   deps = [
     "//base",
     "//components/google/core/browser",
     "//components/search_engines",
     "//url",
   ]
 }
 
 source_set("unit_tests") {
   testonly = true
   sources = [
     "search_android_unittest.cc",
     "search_unittest.cc",
   ]
   deps = [
     ":search",
     "//base",
     "//components/variations",
     "//testing/gtest",
   ]
 }