debian: Also build for sid

Signed-off-by: Stefan Schantl <stefan.schantl@ipfire.org>
Signed-off-by: Michael Tremer <michael.tremer@ipfire.org>

debian/build.sh

 #!/bin/bash
 
 ARCHITECTURES=( amd64 arm64 i386 armhf )
-RELEASES=( buster bullseye )
+RELEASES=( buster bullseye sid )
 
 CHROOT_PATH="/var/tmp"