Compile rtc_base_objc and rtc_api_objc for Mac

webrtc/base/base.gyp

Index: webrtc/base/base.gyp
diff --git a/webrtc/base/base.gyp b/webrtc/base/base.gyp
index f862eae3112b9e93b24e5bcfec6b63db0ff7390b..3eb123b4e4bfd31e703904d06d5c21e42cd32bc0 100644
--- a/webrtc/base/base.gyp
+++ b/webrtc/base/base.gyp
@@ -24,11 +24,12 @@
     }],
     # TODO(tkchin): Mac support. There are a bunch of problems right now because
     # of some settings pulled down from Chromium.
-    ['OS=="ios"', {
+    ['OS=="ios" or OS=="mac"', {
       'targets': [
         {
           'target_name': 'rtc_base_objc',
           'type': 'static_library',
+          'includes': [ '../build/objc_common.gypi' ],
           'dependencies': [
             'rtc_base',
           ],
@@ -57,10 +58,6 @@
               },
             }],
           ],
-          'xcode_settings': {
-            'CLANG_ENABLE_OBJC_ARC': 'YES',
-            'CLANG_WARN_OBJC_MISSING_PROPERTY_SYNTHESIS': 'YES',
-          },
         }
       ],
     }], # OS=="ios"