fix: add back systemd-resolved to buildd images.

systemd-resolved got moved out of the systemd package in kinetic and is
required for bootable buildd environement (as opposed to launchpad buildd)
(LP: #2007419)

live-build/auto/config

@@ -1188,6 +1188,9 @@ case $SUBPROJECT in
 		add_package install build-essential
 		# Needed for LXD-based builds.
 		add_package install init
+		# Needed for bootable buildd systems which don't get injected
+		# nameserver configuration. (LP: 2007419)
+		add_package install systemd-resolved
 		# Not strictly build-essential, but traditionally present
 		# and a variety of things fail without it.
 		add_package install tzdata