I'm assuming /386/bin/fossil/fossil does not, in fact, exist. The fact that the last file completed changes is just a distraction in this case; I suspect you have $NPROC>1 and mk is parallelizing its work. I think if you set NPROC=1 before running mk you'll stop seeing that last file change.
The problem is simply that the kernel mkfiles don't know how to build things in /sys/src/cmd. The trivial work-around is to build fossil yourself (cd /sys/src/cmd/fossil && mk install). There's likely to be other similar binaries needed, so I'd recommend you 'mk install' all of /sys/src/cmd. Anthony
