This would have been commit #2 which was "Obtained from: BSD/OS" except
their code is buggy (they call err() if the execl() fails, which will
incorrectly call exit()), so instead this is:
Obtained from: NetBSD
execvp() in the child branch of a vfork(). Changed to use fork()
instead.
Some of these (mv, find, apply, xargs) might benefit greatly from
being rewritten to use vfork() properly.
PR: Loosely related to bin/8252
Approved by: jkh and bde