Need to resolve how to do build-lock files (and manage them properly) in a charmcraft world

At present, the (soon to be) `add-build-lock-file` replaces the `charmcraft.yaml` with `./global/source-zaza/charmcraft-build-lock-file.yaml` so that a `build.lock` file can be generated in the repo.  It would be nice for stable charms if this was integrated into the master branch of reactive charms such that the tox.ini can handle `add-build-lock-file` directly.