Make two compilation flags for Windows Clang build effective

build_gyp/standalone.gypi

 # Copyright 2014 PDFium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 # Definitions to be used when building stand-alone PDFium binaries.
 
 {
   'variables': {
     'component%': 'static_library',
     'clang%': 0,
@@ skipping 321 matching lines @@
               '/FIIntrin.h',
 
               # TODO(hans): Make this list shorter eventually, http://crbug.com/504657
               '-Qunused-arguments',  # http://crbug.com/504658
               '-Wno-microsoft-enum-value',  # http://crbug.com/505296
               '-Wno-unknown-pragmas',  # http://crbug.com/505314
               '-Wno-microsoft-cast',  # http://crbug.com/550065
             ],
           }],
           ['OS=="win" and clang==1 and MSVS_VERSION == "2013"', {
-            'VCCLCompilerTool': {
-              'AdditionalOptions': [
-                '-fmsc-version=1800',
-              ],
-            },
+            'AdditionalOptions': [
+              '-fmsc-version=1800',
+            ],
           }],
           ['OS=="win" and clang==1 and MSVS_VERSION == "2015"', {
-            'VCCLCompilerTool': {
-              'AdditionalOptions': [
-                '-fmsc-version=1900',
-              ],
-            },
+            'AdditionalOptions': [
+              '-fmsc-version=1900',
+            ],
           }],
         ],
       },
       'VCLibrarianTool': {
         'AdditionalOptions': ['/ignore:4221'],
       },
       'VCLinkerTool': {
         'GenerateDebugInformation': 'true',
         'LinkIncremental': '1',
         # SubSystem values:
@@ skipping 137 matching lines @@
       ],
     }],  # OS=="win"
     ["use_goma==1", {
       'make_global_settings': [
         ['CC_wrapper', '<(gomadir)/gomacc'],
         ['CXX_wrapper', '<(gomadir)/gomacc'],
       ],
     }],  # use_goma==1
   ],
 }