zfsboot: Remove zfsboot(8) program used to boot ZFS from MBR + BIOS

[jhb]

Summary

This has not worked since the import of OpenZFS in FreeBSD 13.0.
Trying to fix it at this point would probably entail rearchitecting
how it works (e.g. using a dedicated freebsd-boot slice to hold
zfsboot). However, it's not really worth doing that at this point.

PR: 271262
Reported by: Henryk Paluch <[e-mail]>

[jhb]

Note that stand/i386/zfsboot/zfsboot.c remains as it is used by gptzfsboot. Possibly zfsboot.c should just move into the gptzfsboot/ directory?

[imp]

In D51545#1177172, @jhb wrote:

Note that stand/i386/zfsboot/zfsboot.c remains as it is used by gptzfsboot. Possibly zfsboot.c should just move into the gptzfsboot/ directory?

I'd move it. I just took a quick look and don't think that more than a Makefile adjustment (to remove the path) and a git mv will be needed.

[imp]

tools/boot/rootgen.sh

278

This, and the rest of the file. Just as well... I had it working before the OpenZFS import (I think, it's been a while and I got it working long enough to test this script), but haven't really tested it since. It was, as you can see, the ugliest thing I had to do to get to 'support all boot environments.