However it takes 24 minutes even to build ancient small emacs-18.59. simh emulating microvax3900 on my i5-4570 NetBSD/amd64 took ~70 hours to build perl 5.38.2 (from pkgsrc-2023Q4) so it won't finish in 6 hour github CI limit.
My fastest machine, a Ryzen 7900, takes just about 7.5 hours to compile perl-5.40.0nb1 (open-simh 4.1.0, NetBSD 10/amd64, NetBSD 10.1/vax, latest pkgsrc). While I wasn't expecting it to be under six hours, I certainly didn't think it'd be nine times faster in single core performance than an Intel i5-4570.
I don't know how fast the CI worker is, but I suspect it's not quite as fast. Still, it does seem that it's possible to extend the time as discussed here:
https://github.com/orgs/community/discussions/26679 John