Move gn secondary_source to the build/ directory

tools/gn/secondary/third_party/android_tools/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.
-
-config("cpu_features_include") {
-  include_dirs = [ "ndk/sources/android/cpufeatures" ]
-}
-
-# This is the GN version of
-# //build/android/cpufeatures.gypi:cpufeatures
-source_set("cpu_features") {
-  sources = [ "ndk/sources/android/cpufeatures/cpu-features.c" ]
-  direct_dependent_configs = [ ":cpu_features_include" ]
-
-  configs -= [ "//build/config/compiler:chromium_code" ]
-  configs += [ "//build/config/compiler:no_chromium_code" ]
-}