Mkhash not getting built

It has just dawned on me that the patches required to make mkhash when run on FreeBSD were actually incorporated a year ago:-;a=commit;h=1db9b5b6d65052eea7819cf0aee5163846a36bed

but having just tried it mkhash frequently fails to get built. How can I see why it fails?

This is the sort of error I get:-

Prerequisite check failed. Use FORCE=1 to override.
gmake: *** [/root/OpenWrt-BuildSystem/openwrt/include/ staging_dir/host/.prereq-build] Error 1
bash: line 3: /root/OpenWrt-BuildSystem/openwrt/staging_dir/host/bin/mkhash: No such file or directory