Make installworld fails on file not found (Error code 71)

I was trying to test the new i915 graphics driver but got stuck in building and installing the userland:

/usr/share/man/man2/mknodat.2 -> /usr/share/man/man2/mknod.2
/usr/share/man/man2/munlock.2 -> /usr/share/man/man2/mlock.2
/usr/share/man/man2/munlockall.2 -> /usr/share/man/man2/mlockall.2
/usr/share/man/man2/modfnext.2 -> /usr/share/man/man2/modnext.2
/usr/share/man/man2/nmount.2 -> /usr/share/man/man2/mount.2
/usr/share/man/man2/unmount.2 -> /usr/share/man/man2/mount.2
/usr/share/man/man2/mq_timedreceive.2 -> /usr/share/man/man2/mq_receive.2
/usr/share/man/man2/mq_timedsend.2 -> /usr/share/man/man2/mq_send.2
/usr/share/man/man2/ntp_gettime.2 -> /usr/share/man/man2/ntp_adjtime.2
/usr/share/man/man2/numa_setaffinity.2 -> /usr/share/man/man2/numa_getaffinity.2
install: link /usr/share/man/man2/numa_getaffinity.2 -> /usr/share/man/man2/numa_setaffinity.2: No such file or directory
*** Error code 71

Stop.
make[5]: stopped in /usr/src/lib/libc
*** Error code 1

Stop.
make[4]: stopped in /usr/src/lib
*** Error code 1

Stop.
make[3]: stopped in /usr/src
*** Error code 1

Stop.
make[2]: stopped in /usr/src
*** Error code 1

Stop.
make[1]: stopped in /usr/src
*** Error code 1

Stop.
make: stopped in /usr/src


Now I have a new kernel on a userland dating to last April 27.

I got this same result with "make installworld" also on previous attempt just a day previous.

Do I need to clean out old build directory tree?  Build runs cleandir automatically, but do I need more, like rm -R /usr/obj/* ?

If this happened in NetBSD, I would use -r with build.sh which gets rid of outdated stuff in build directories, and will get a chance to try this as I try to update a system last built 14 months ago.

What do I need to do in FreeBSD?

Tom