architectures: Add a watchdog timer

Oddly, ARM is okay with an Intel WDT.

Signed-off-by: Andy Lutomirski <luto@amacapital.net>
virtme-udhcpc-script: Switch to bash

This script contains bashisms; require bash.

Signed-off-by: Andy Lutomirski <luto@amacapital.net>
virtme-init: Implement virtme_chdir

This will allow the host to set the guest's initial working directory.

Signed-off-by: Andy Lutomirski <luto@amacapital.net>