If any --docdir is passed, the app can't find the builtin documentation
Just inherit docdir from configure now, which defaults to the same thing
but if overridden will act proper now.
Related: https://bugs.gentoo.org/813438
Signed-off-by: Marco Sirabella <marco@sirabella.org>
Signed-off-by: Lukas Fleischer <lfleischer@calcurse.org>
