HEADSUP: Something has gone south with -current

Dell 7510 laptop was happily running FreeBSD12-alpha9
from Oct. 10th.  I decided to update to top-of-tree
today, which would be FreeBSD13 at r341703.

% cd /usr/obj
% rm -rf usr
% cd ../src
% svn update
% make -j6 buildwould   (OK)
% make -j6 buildkernel  (OK)
% make installkernel    (OK)
% mergemaster -p
% <reboot into single user mode>
% mount -a
% cd /usr/src
% make installworld

Dies with a segfault in make(1) half way through the update.
/sbin has been update.

Rebooted with new kernel. Laptop locks up.
Rebooted with kernel.old/kernel (known good kernel).  Laptop locks up.
Rebooted with verbose info.  Lockup occurs right after

Starting /sbin/init

is printed to console.

Reboot to Dell laptop BIOS and run system diagnostics.

Reboot with old FreeBSD installation cdrom.  Mounted the
laptop's root filesystem on /mnt.

% chflags nochgs /mnt/sbin/init
% cp /mnt/sbin/init.bak /mnt/sbin/init

Reboot laptop and finally get back to multi-user mode.  Post trauma
analysis

make core dumps.
devd core dumps.
init core dumps.
cc   core dumps.  
c++  core dumps.

Something seems to be broken.

-- 
Steve