Remove hotword installation code at compile time if hotwording disabled.

build/common.gypi

 # Copyright (c) 2012 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.
 
 # IMPORTANT:
 # Please don't directly include this file if you are building via gyp_chromium,
 # since gyp_chromium is automatically forcing its inclusion.
 {
   # Variables expected to be overriden on the GYP command line (-D) or by
   # ~/.gyp/include.gypi.
@@ skipping 2708 matching lines @@
       }],
       ['remoting==1', {
         'defines': ['ENABLE_REMOTING=1'],
       }],
       ['enable_webrtc==1', {
         'defines': ['ENABLE_WEBRTC=1'],
       }],
       ['enable_media_router==1', {
         'defines': ['ENABLE_MEDIA_ROUTER=1'],
       }],
+      ['enable_hotwording==1', {
+        'defines': [ 'ENABLE_HOTWORDING' ],
+      }],
       ['proprietary_codecs==1', {
         'defines': ['USE_PROPRIETARY_CODECS'],
         'conditions': [
           ['enable_mpeg2ts_stream_parser==1', {
             'defines': ['ENABLE_MPEG2TS_STREAM_PARSER'],
           }],
         ],
       }],
       ['enable_viewport==1', {
         'defines': ['ENABLE_VIEWPORT'],
@@ skipping 3470 matching lines @@
     # settings in target dicts.  SYMROOT is a special case, because many other
     # Xcode variables depend on it, including variables such as
     # PROJECT_DERIVED_FILE_DIR.  When a source group corresponding to something
     # like PROJECT_DERIVED_FILE_DIR is added to a project, in order for the
     # files to appear (when present) in the UI as actual files and not red
     # red "missing file" proxies, the correct path to PROJECT_DERIVED_FILE_DIR,
     # and therefore SYMROOT, needs to be set at the project level.
     'SYMROOT': '<(DEPTH)/xcodebuild',
   },
 }