msvs/ninja win: Fix support for ImageHasSafeExceptionHandlers

test/win/linker-flags/safeseh.gyp

 # Copyright (c) 2014 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.
 
 {
  'targets': [
     {
       'target_name': 'test_safeseh_default',
       'type': 'executable',
       'msvs_settings': {
+        # By default, msvs passes /SAFESEH for Link, but not for MASM.  In
+        # order for test_safeseh_default to link successfully, we need to
+        # explicitly specify /SAFESEH for MASM.
+        'MASM': {
+          'UseSafeExceptionHandlers': 'true',
+        },
       },
       'sources': [
         'safeseh_hello.cc',
         'safeseh_zero.asm',
       ],
     },
     {
       'target_name': 'test_safeseh_no',
       'type': 'executable',
       'msvs_settings': {
@@ skipping 17 matching lines @@
           'UseSafeExceptionHandlers': 'true',
         },
       },
       'sources': [
         'safeseh_hello.cc',
         'safeseh_zero.asm',
       ],
     },
   ]
 }