On a fresh installed system, i got that error when i try to execute bitkeeper:
Error, link "/usr/local/bin/bk->../bitkeeper/bk" must be a full path name
% uname -a
FreeBSD freeb 12.1-RELEASE-p5 FreeBSD 12.1-RELEASE-p5 GENERIC amd64
I see the problem. Line 216 of platforminit.c. It's doing some funky stuff with the pathname.