Fix xcode 4.1 build issue

http://codereview.appspot.com/5992048/



git-svn-id: http://skia.googlecode.com/svn/trunk@3621 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/gyp/common_conditions.gypi b/gyp/common_conditions.gypi
index 7152181..cfb67ae 100644
--- a/gyp/common_conditions.gypi
+++ b/gyp/common_conditions.gypi
@@ -126,6 +126,7 @@
           },
         },
         'xcode_settings': {
+          'GCC_SYMBOLS_PRIVATE_EXTERN': 'NO',
           'SYMROOT': '<(DEPTH)/xcodebuild',
           'SDKROOT': 'macosx10.6',
 # trying to get this to work, but it needs clang I think...