It’s the more-or-less unreleased CLI compiler. You can read about it here and here.
As noted, it is a first step toward addressing your problem, but there remains work to be done.
As we discussed, you can do this today with PackageCompiler; it just probably won’t be small. I would hazard to guess that, if you can get it working that way, the forthcoming compiler improvements will continue to make the process and results better.