buildkernel: Cleaning for nvidia-driver-470-470.161.03: [all] Stopped -- signal 22

From: Graham Perrin <grahamperrin_at_gmail.com>
Date: Sat, 16 Sep 2023 05:30:30 UTC
The tail of a log:

…
Building /usr/obj/usr/src/amd64.amd64/sys/GENERIC/kernel.full
--- kernel.full ---
linking kernel.full
ctfmerge -L VERSION -g -o kernel.full ...
       text      data        bss        dec         hex   filename
   20670038   1677321   19288064   41635423   0x27b4e5f kernel.full
Building /usr/obj/usr/src/amd64.amd64/sys/GENERIC/kernel.debug
Building /usr/obj/usr/src/amd64.amd64/sys/GENERIC/kernel
--- all ---
===> Ports module x11/nvidia-driver-470 (all)
cd /usr/ports/x11/nvidia-driver-470; env  -u CC  -u CXX  -u CPP -u 
MAKESYSPATH  -u MK_AUTO_OBJ  -u MAKEOBJDIR  MAKEFLAGS="-j 32 -J 15,16 -j 
32 -J 15,16 -D NO_MODULES_OBJ DISABLE_VULNERABILITIES=yes KERNEL=kernel 
TARGET=amd64 TARGET_ARCH=amd64" SYSDIR=/usr/src/sys 
PATH=/usr/obj/usr/src/amd64.amd64/tmp/bin:/usr/obj/usr/src/amd64.amd64/tmp/usr/sbin:/usr/obj/usr/src/amd64.amd64/tmp/usr/bin:/usr/obj/usr/src/amd64.amd64/tmp/legacy/usr/sbin:/usr/obj/usr/src/amd64.amd64/tmp/legacy/usr/bin:/usr/obj/usr/src/amd64.amd64/tmp/legacy/bin:/usr/obj/usr/src/amd64.amd64/tmp/legacy/usr/libexec::/sbin:/bin:/usr/sbin:/usr/bin:/usr/local/bin:/usr/local/sbin 
SRC_BASE=/usr/src  OSVERSION=1500000 
WRKDIRPREFIX=/usr/obj/usr/src/amd64.amd64/sys/GENERIC make -B clean build
===>  Cleaning for nvidia-driver-470-470.161.03
*** [all] Stopped -- signal 22

----

Why might a stop occur, with that signal?

My src.conf included:

PORTS_MODULES+=x11/nvidia-driver-470