Adds a fallback option if Firebase SDK zip fails to download successfully.
Adds a fallback option if Firebase SDK zip fails to download successfully.

PiperOrigin-RevId: 139260458

FirebaseExtended/cocos2dx-cpp-sample,FirebaseExtended/cocos2dx-cpp-sample,FirebaseExtended/cocos2dx-cpp-sample,FirebaseExtended/cocos2dx-cpp-sample