arch-nspawn: remove leading - from the machine name/hostname

Signed-off-by: Florian Pritz <bluewind@xinu.at>
Signed-off-by: Pierre Schmitz <pierre@archlinux.de>

arch-nspawn.in

@@ -98,8 +98,11 @@ copy_hostconf
 
 eval $(grep '^CARCH=' "$working_dir/etc/makepkg.conf")
 
+machine_name="${working_dir//\//-}"
+machine_name="${machine_name#-}"
+
 exec ${CARCH:+setarch "$CARCH"} systemd-nspawn 2>/dev/null \
 	-D "$working_dir" \
-	--machine "${working_dir//\//-}" \
+	--machine "$machine_name" \
 	"${mount_args[@]}" \
 	"$@"