Base builds fine.
Exp-Run requested in https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=245027
The Makefile.inc1 and Makefile.libcompat can probably be committed right now.
This part can probably be committed straight away
I wasn't sure about committing in 2 parts but @imp points out that's beneficial for MFC - so yeah, let's commit the disuse of these libs first.
Update after r359324
These two are MFCable I think?
TBH I didn't planned to mfc anything on this review.
I guess those too could be mfc but I haven't tested anything on 12.
OK - I would commit them separately anyhow so that they could be MFC'd if someone is so inclined, even if you don't tag them as MFC or intend to do so.