lfs_fs_mkconsistent allows running the internal consistency operations
(desuperblock/deorphan/demove) on demand and without any other
filesystem changes.
This can be useful for front-loading and persisting consistency operations
when you don't want to pay for this cost on the first write to the
filesystem.
Conveniently, this also offers a way to force the on-disk minor version
to bump, if that is wanted behavior.
Idea from kasper0
259535ee73