port build fails with missing sys/smr_types.h

Hi

I'm trying to fix the build of qemu-utils but am seeing failures on
CURRENT (13.0-HEAD-9e082d278b9) like:

In file included from util/oslib-posix.c:50:
In file included from /usr/include/sys/user.h:51:
In file included from /usr/include/sys/proc.h:50:
/usr/include/sys/filedesc.h:47:10: fatal error: 'sys/smr_types.h' file not found
#include <sys/smr_types.h>
         ^~~~~~~~~~~~~~~~~

# uname -a
FreeBSD sv0.tuffli.net 13.0-HEAD-9e082d278b9 FreeBSD
13.0-HEAD-9e082d278b9 #0 9e082d278b91-c254726(HEAD)-dirty: Fri Nov 27
00:09:50 PST 2020
root_at_freebsd:/build/9e082d278b9/obj/build/9e082d278b9/src/amd64.amd64/sys/GENERIC-NODEBUG
 amd64
# ls -l /usr/include/sys/*smr*
-r--r--r--  1 root  wheel  1988 Nov 30 14:04 /usr/include/sys/_smr.h
-r--r--r--  1 root  wheel  7822 Nov 30 14:04 /usr/include/sys/smr.h

So it appears the file is missing. Any ideas?

--chuck