sys/capability.h will be removed before FreeBSD 13. The (now) correct header to use on all supported (and most unsupported) versions of FreeBSD is sys/capsicum.h.
There's no need for autoconf checks etc. to check for both (in the ports tree) but upstream may want to if there's a desire to build on older releases.
It appears this is simply a side-effect of go's use of capability.h - see PR 233092.
(In reply to Ed Maste from comment #1)
so if this is a GO problem, can we close this issue?
Or is there any need for gitlab-shell?
(In reply to Matthias Fechner from comment #2)
We'll probably still need to patch devel/gitlab-shell until the change makes its way into a new release.
A grep through the source shows it is changed to capsicum.h, I think we can close here.