mkfontdir.cpp refers to mkfontscale as BINDIR/mkfontscale. This breaks if mkfontscale is installed in a different prefix, as it may be since they are packaged separately. This would work in a wider variety of setups:
exec mkfontscale ...
Author: Jeremy Huddleston <firstname.lastname@example.org>
Date: Thu Oct 6 10:29:42 2011 -0700
Fix issues where mkfontscale and mkfontdir are installed in different
locations or bindir contains a space
Signed-off-by: Jeremy Huddleston <email@example.com>
on Jul 02, 2016 at 07:22:24.
(provided by the Example extension).