Disaster recovery after panic while doing installworld

This morning I was installing a new system on my Alder Lake laptop and it
panicked while doing installworld. After the panic, it would not boot,
reporting that there was an unknown symbol in /boot/lua/config.lua line 1.

I hope to recover it by booting  a live system from a main snapshot, but I
am uncertain of what environmental variables I will need to set to convince
the system to make installworld from the /usr/obj on /mnt and install into
/mnt.

Any suggestions?
-- 
Kevin Oberman, Part time kid herder and retired Network Engineer
E-mail: rkoberman@gmail.com
PGP Fingerprint: D03FB98AFA78E3B78C1694B318AB39EF1B055683