Call Python version of oilplan plugin flags script.

Source/config.gyp

Index: Source/config.gyp
diff --git a/Source/config.gyp b/Source/config.gyp
index 05b671da4a3b419ad9de198b3122582f3c61f584..8a801ad6c6e076e905da35e0364611a76d234118 100644
--- a/Source/config.gyp
+++ b/Source/config.gyp
@@ -102,9 +102,14 @@
         }],
         # Only enable the blink_gc_plugin when using clang and chrome plugins.
         ['blink_gc_plugin==1 and clang==1 and clang_use_chrome_plugins==1', {
-          'cflags': ['<!@(../../../tools/clang/scripts/blink_gc_plugin_flags.sh enable-oilpan=<(enable_oilpan) <(blink_gc_plugin_flags))'],
+          'cflags': ['<!@(python ../../../tools/clang/scripts/blink_gc_plugin_flags.py enable-oilpan=<(enable_oilpan) <(blink_gc_plugin_flags))'],
           'xcode_settings': {
-            'OTHER_CFLAGS': ['<!@(../../../tools/clang/scripts/blink_gc_plugin_flags.sh enable-oilpan=<(enable_oilpan) <(blink_gc_plugin_flags))'],
+            'OTHER_CFLAGS': ['<!@(python ../../../tools/clang/scripts/blink_gc_plugin_flags.py enable-oilpan=<(enable_oilpan) <(blink_gc_plugin_flags))'],
+          },
+          'msvs_settings': {
+            'VCCLCompilerTool': {
+              'AdditionalOptions': ['<!@(python ../../../tools/clang/scripts/blink_gc_plugin_flags.py enable-oilpan=<(enable_oilpan) <(blink_gc_plugin_flags))'],
+            },
           },
         }],
         ['blink_disable_partition_allocator==1', {