find: fix pathnames printed by the SIGINFO handler

Don't duplicate the last component.

PR: 290362
Reported by: John F. Carr <jfc@mit.edu>
Fixes: d06a00963b7
Reviewed by: jilles, Goran Mekić <meka@tilda.center>
Pull Request: https://github.com/freebsd/freebsd-src/pull/1878

(cherry picked from commit f6d767fe862964f704baf4eb388a30ed8227bb65)