Use precompiled headers on Windows only when a flag is set.

build/win_precompile.gypi

 # Copyright (c) 2011 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.
 
 # Include this file to make targets in your .gyp use the default
 # precompiled header on Windows, in debug builds only as the official
 # builders blow up (out of memory) if precompiled headers are used for
 # release builds.
 
 {
   'conditions': [
-    ['OS=="win"', {
+    ['OS=="win" and win_use_pch==1', {
         'target_defaults': {
-          'configurations': {
-            'Debug': {
-              'msvs_precompiled_header': '<(DEPTH)/build/precompile.h',
-              'msvs_precompiled_source': '<(DEPTH)/build/precompile.cc',
-            },
-          },
-
-          # Sources can't be specified inside the 'Debug'
-          # configuration. Since precompile.cc only contains
-          # comments, it won't have any effect for 'Release' builds.
+          'msvs_precompiled_header': '<(DEPTH)/build/precompile.h',
+          'msvs_precompiled_source': '<(DEPTH)/build/precompile.cc',
           'sources': ['<(DEPTH)/build/precompile.cc'],
         }
       }],
   ],
 }