main/postmarketos-base-ui: add coreutils as dependency

People running UIs should not have to depend on basic utilities from busybox such as non-portable /usr/bin/env. Total size is 1176KiB, which should be marginal compared to any UI installation.

This came up in a discussion with @sonnyp, related to this issue[[1] in an app he maintains. Like really, we should not be starting something with busybox to save 1MiB

[1] https://github.com/sonnyp/Tangram/issues/236

main/postmarketos-base-ui/APKBUILD

 # Maintainer: Clayton Craft <clayton@craftyguy.net>
 pkgname=postmarketos-base-ui
 pkgver=6
-pkgrel=2
+pkgrel=3
 pkgdesc="Meta package for minimal postmarketOS UI base"
 url="https://postmarketos.org"
 arch="noarch"
 license="GPL-3.0-or-later"
 depends="
 	chrony
+	coreutils
 	dbus
 	font-dejavu
 	haveged