The issue is that use/fonts/infinality doesn't actually
require the script hook thus registering the feature's
name in FEATURES variable so that the feature's contents
get copied over is not neccessary (distcfg.mk build-up
will have happened anyways).

But that's confusing if one's forgot this peculiarity
(like me today) or never knew of it, so let's spare
some frustration.

Thanks cow@ for both the packages and suggestion.

This includes an updated version of 50-fontconfig script
which actually works (the preliminary one attached to #28612
didn't); thanks zerg@ and cow@ for providing the incentive
to introduce it.

Based on m-p-d and installer-feature-kdesktop-fontconfig.