Change some source_sets to static_library to shrink binary

src/trusted/validator_x86/BUILD.gn

 # Copyright (c) 2014 The Native ClientAuthors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import("//native_client/src/trusted/asm.gni")
 
 if (current_cpu == "x86" || current_cpu == "x64") {
   if (current_toolchain == nacl_asm_toolchain) {
     source_set("nccopy_asm") {
       sources = [
         "nccopycode_stores.S",
       ]
       deps = [
         "//build/config/nacl:nacl_base",
       ]
     }
   }
 
-  source_set("nccopy") {
+  static_library("nccopy") {
     sources = [
       "nccopycode.c",
     ]
     deps = [
       "//build/config/nacl:nacl_base",
       ":nccopy_asm($nacl_asm_toolchain)",
     ]
   }
 }