mkosi: make sure /run and /tmp are empty in the disk image
mkosi: make sure /run and /tmp are empty in the disk image

Let's mount a tmpfs to /run and /tmp while we put together the image, so
that anything the install scripts install there does not end up in the
disk image.

UbiCastTeam/mkosi,systemd/mkosi,UbiCastTeam/mkosi,systemd/mkosi