Fix precompiled header test

test/msvs/precompiled/hello.gyp

Index: test/msvs/precompiled/hello.gyp
diff --git a/test/msvs/precompiled/hello.gyp b/test/msvs/precompiled/hello.gyp
index b9533efd851c0881b6eb8b57956db812cb36a2a8..5f82c535939eacf0f07b2f13029f54eb333fd962 100644
--- a/test/msvs/precompiled/hello.gyp
+++ b/test/msvs/precompiled/hello.gyp
@@ -1,4 +1,4 @@
-# Copyright (c) 2011 Google Inc. All rights reserved.
+# Copyright (c) 2012 Google Inc. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
@@ -14,6 +14,15 @@
       ],
       'msvs_precompiled_header': 'stdio.h',
       'msvs_precompiled_source': 'precomp.c',
+
+      # Required so that the printf actually causes a build failure
+      # if the pch isn't included.
+      'msvs_settings': {
+        'VCCLCompilerTool': {
+          'WarningLevel': '3',
+          'WarnAsError': 'true',
+        },
+      },
     },
   ],
 }