reproducible Debian: devscripts from buster-bpo is uninstallable on Ubuntu 16.04

Signed-off-by: Holger Levsen <holger@layer-acht.org>

hosts/common-arm64/etc/apt/sources.list

@@ -4,9 +4,8 @@ deb http://gb.ports.ubuntu.com/ubuntu-ports/ xenial-backports main universe
 
 deb http://ports.ubuntu.com/ubuntu-ports xenial-security main universe
 
-# we're using some stretch- and buster-backports on these old 16.04 LTS systems
+# we're using some stretch-backports on these old 16.04 LTS systems
 deb http://deb.debian.org/debian/ stretch-backports main
-deb http://deb.debian.org/debian/ buster-backports main
 
 # for debian-archive-keyring
 deb http://gb.ports.ubuntu.com/ubuntu-ports/ eoan main universe

update_jdn.sh

@@ -254,7 +254,7 @@ if [ -f /etc/debian_version ] ; then
 			debian-archive-keyring
 			cdebootstrap-
 			debootstrap
-			devscripts/buster-backports
+			devscripts
 			eatmydata
 			etckeeper
 			figlet
@@ -306,7 +306,11 @@ if [ -f /etc/debian_version ] ; then
 				pbuilder/stretch-backports
 				" ;;
 			*)	# not available in Ubuntu 16.04:
-				DEBS="$DEBS ripgrep mmdebstrap"
+				DEBS="$DEBS
+				ripgrep
+				mmdebstrap
+				devscripts/buster-backports
+				" ;;
 		esac
 		case $HOSTNAME in
 			# needed for rebuilding Debian (using .buildinfo files)