gtk-update-icon-cache getting called with DESTDIR
Distro packaging relies on applications to not call gtk-update-icon-cache themselves when DESTDIR is set. Most apps honor this (the hook is only ran if DESTDIR is unset), but for some reason balsa explicitly made it run with DESTDIR too in commit 6642a029 with a follow-up commit 422efc1b
This is bad, please make it conditional and not run it if DESTDIR is set. As-is I need to apply hacks or local patches in my Gentoo package.