Enable more targets in the Android GN build.

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" ]
 }