Panic while making buildlernel on RPi3

For the first time a panic has occurred while making buildkernel
on an RPi3. The same machine successfully ran stress2's misc/all.sh
test suite for a couple of days, so I'm surprised. Granted, that was
a few updates ago and this is on -current, but still..... buildkernel
is not the trigger expected.

The backtrace and build logs are at 
http://www.zefox.net/~fbsd/rpi3/crashes/20220304/readme
but unfortunately I didn't anticipate trouble and so didn't
capture very much.

Hope this is of some interest, thanks for reading.

bob prohaska