execute the build scripts after a build

this is useful if backports were done during a build
so instead of waiting a few hours for the cron job to run
again, they will be built a few minutes after the previous batch

As signing is a manual step, regrouping packages batch reduce
the work for people signing the packages, and reduce the time to
deliver to end user

cron.sh

@@ -21,6 +21,7 @@ then
 	set -e
 	./10_start_remote.sh
 	./07_send_mail_global.sh
+        exec sh cron.sh
 else
 	echo "nothing to do"
 fi