* SSH block device support is dropped until we ship libssh (upstream
  switched away from libssh2)
* system-ppcemb target dropped upstream
* Switched to user/libslirp (4.2.0) instead of vendored copy (4.1.0)
  which fixes several CVEs (included in these secfixes for this time
  only; future secfixes for libslirp should be in user/libslirp with a
  rebuild of qemu for the statically linked bits).

paxmark doesn't support tmpfs.

The corresponding binaries are currently part of the generic "qemu" package.

It's currently an automagic dep, and linking against both nettle and
gcrypt may be problematic.