Draft: debvm-run: support hurd

Would it be funny if debvm-run could run a disk image for hurd?

This is just a placeholder MR as it is still blocked by a few patches to be integrated so that it's possible to create a chrootless hurd image. So far, I just added a working qemu cmdline so that future-me knows what to do. There are a few issues.

• should debvm-create support hurd as well? If yes, it should probably run mmdebstrap chrootless wrapped inside another mmdebstrap which would add significantly to the complexity of debvm-run i think. Maybe mmdebstrap should contain that complexity instead?
• extracting the mach kernel means that one has to know its version as there is no symlink to /boot/gnumach-1.8-486.gz
• in addition to the kernel, at least /hurd/ext2fs.static and /hurd/exec.static also have to be copied to the outside -- more complexity

I have no personal use for hurd. I just find it interesting to get working. 😄

What do you think?

EDIT: relevant tips for hurd in qemu: https://darnassus.sceen.net/~hurd-web/hurd/running/qemu/