Make it possible to enable blink_gc_plugin on mac.

We were missing the xcode_settings OTHER_CFLAGS.

R=oilpan-reviews@chromium.org, tkent@chromium.org, zerny@chromium.org
BUG=

Review URL: https://codereview.chromium.org/214403002

git-svn-id: svn://svn.chromium.org/blink/trunk@170222 bbb929c8-8fbe-4397-9dbb-9b2b20218538

third_party/WebKit/Source/config.gyp

@@ -107,6 +107,9 @@
         # 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) dump-graph=<(blink_gc_plugin_dump_graph))'],
+          'xcode_settings': {
+            'OTHER_CFLAGS': ['<!@(../../../tools/clang/scripts/blink_gc_plugin_flags.sh enable-oilpan=<(enable_oilpan) dump-graph=<(blink_gc_plugin_dump_graph))'],
+          },
         }],
       ],
     },