disable symbols hiding in Mac release builds

Author: collinjackson

cocos2d.xcodeproj/project.pbxproj

@@ -3732,6 +3732,7 @@
 				DEBUG_INFORMATION_FORMAT = "dwarf-with-dsym";
 				ENABLE_NS_ASSERTIONS = NO;
 				EXECUTABLE_PREFIX = lib;
+				GCC_SYMBOLS_PRIVATE_EXTERN = NO;
 				GCC_TREAT_WARNINGS_AS_ERRORS = NO;
 				GCC_WARN_ABOUT_RETURN_TYPE = YES_ERROR;
 				GCC_WARN_UNINITIALIZED_AUTOS = YES;