Support building images out of kali-last-snapshot

auto/config

@@ -85,6 +85,16 @@ case "$arch" in
     ;;
 esac
 
+# Define options that vary across distributions
+case "$dist" in
+    kali-last-snapshot)
+	# We don't want kali-last-snapshot to end up in the image, it
+	# should be replaced with kali-rolling
+	lb_opts="$lb_opts --distribution-binary kali-rolling"
+	lb_opts="$lb_opts --debootstrap-script /usr/share/debootstrap/scripts/kali-rolling"
+    ;;
+esac
+
 # Setup configuration files from variant and options
 
 # Drop all files that a former run might have put into place