FreeBSD CI

[b-NC]

Describe the solution you'd like
I would like to provide a few FreeBSD runners for swift to be tested on

I have hardware that runs FreeBSD laying around (namely, older hp rack servers) that are running FreeBSD and I would like to provide a bit of computing power 😃

[b-NC]

(I would also enjoy working on making swift work a bit better on freebsd)

[finagolfin]

I suggest you look at updating the open FreeBSD pull #38335 and follow in the footsteps of the current OpenBSD support from @3405691582. If you have any questions, don't hesitate to ask us.