I think it would be nice, if the libs are just linked to a certain branch instead of including them (it could be easier to update them). The unneeded stuff (like the examples) can be excluded in addon_config.make.
Sadly I am not sure how to do that.
https://stackoverflow.com/questions/59810010/how-should-i-link-to-library-dependencies-from-my-git-repository
Like they do it with Pure Data in libpd: https://github.com/libpd/libpd