Hi there,
We do not currently do this; as you note, we run only a single level submodule clone, doing something like this:
git pull <your repo> ; cd your-repo ; git submodule update -f --init
so we won’t get the 2+ deep submodules.
You’ll need to do something different there, like clone your own sub-submodules before building, which is pretty complicated unless they are public repos. See this article for details:
I’ve added your voice to our open feature request on better submodule clones, so I’ll follow up in this thread in case we change that behavior. I do not expect a change anytime soon though, so if you want to use our service, probably best to find a workaround.