- When fltk is not installed, scripts/check-fltk-threads.sh misbehaves
due to not checking existence of fltk-config before using it. Fix that
by checking existence before using.
PR: ports/116623
Submitted by: bgruber <knightbg at yahoo.com>
Approved by: Martin Tournoij <carpetsmoker at xs4all.nl> (maintainer)