amber-phone-staging: add debug packge repos

We skip amber-phone-debug for the moment since it does not exist

conf/dists/amber-phone-staging

@@ -4,5 +4,8 @@ deb https://repo.pureos.net/pureos amber-updates main
 deb https://repo.pureos.net/pureos amber-security main
 deb https://repo.pureos.net/pureos amber-phone main
 deb https://repo.pureos.net/pureos amber-phone-staging main
+
+deb http://repo.pureos.net/pureos-debug/ amber-debug main
+deb http://repo.pureos.net/pureos-debug/ amber-phone-staging-debug main
 "
 debootstrap_dist=amber