Segfault during build of accf_dns.ko.full

This has now happened for 2 (different, but still amd64/GENERIC)
machines, so it appears to be reproducible.

The first was a 32-core headless build machine; the second is a laptop.
In each case, the machine had been running main-n290715-feab010f4414
(product of yesterday's daily tracking) and the sources had been updated
to main-n290746-6d5c80aee3ae this morning; "make buildworld" had
succeeded, and "make buildkernel" was in progress.

The build typescript from each machine shows:
...
>>> stage 1: configuring the kernel
...
>>> stage 2.3: build tools
...
>>> stage 3.1: building everything
...
*** [accf_data.ko.full] Error code 139
make[4]: *** accf_data.ko.full removed
...
make[4]: stopped making "all" in /usr/src/sys/modules/accf_data
.ERROR_TARGET='accf_data.ko.full'
.ERROR_META_FILE='/common/S4/obj/usr/src/amd64.amd64/sys/GENERIC/modules/usr/src/sys/modules/accf_data/accf_data.ko.full.meta'
.MAKE.LEVEL='4'
MAKEFILE=''
.MAKE.MODE='meta missing-filemon=yes missing-meta=yes silent=yes verbose'
_ERROR_CMD='ld -m elf_x86_64_fbsd -warn-common --build-id=sha1 -T /usr/src/sys/conf/ldscript.kmod.amd64 -r  -o accf_data.ko.full accf_data.o ; ctfmerge -L VERSION -g -o accf_data.ko.full accf_data.o ; :> export_syms; awk -f /usr/src/sys/conf/kmod_syms.awk accf_data.ko.full  export_syms | xargs -J % objcopy % accf_data.ko.full;'
....

The ERROR_META_FILE has:

# Meta data file /common/S4/obj/usr/src/amd64.amd64/sys/GENERIC/modules/usr/src/sys/modules/accf_data/accf_data.ko.full.meta
CMD ld -m elf_x86_64_fbsd -warn-common --build-id=sha1 -T /usr/src/sys/conf/ldscript.kmod.amd64 -r  -o accf_data.ko.full accf_data.o
CMD ctfmerge -L VERSION -g -o accf_data.ko.full accf_data.o
CMD :> export_syms
CMD awk -f /usr/src/sys/conf/kmod_syms.awk accf_data.ko.full  export_syms | xargs -J % objcopy % accf_data.ko.full
CWD /common/S4/obj/usr/src/amd64.amd64/sys/GENERIC/modules/usr/src/sys/modules/accf_data
TARGET accf_data.ko.full
OODATE accf_data.o
-- command output --
Segmentation fault

*** Error code 139

-- filemon acquired metadata --
....

I will attach a copy of the file 9from the headless build machine)
for reference.

Oh: I see that the typescripts are now showing a warning that I had not
recalled seeing until recently -- e.g.:

make[1]: /usr/src/Makefile.inc1:380: warning: Warning: buildkernel should not be run as root

Peace,
david
-- 
David H. Wolfskill                              david@catwhisker.org

See https://www.catwhisker.org/~david/publickey.gpg for my public key.