scripts: Add next-kernel-number

add scripts/next-kernel-number which just outputs the next free kernel
build number.

scripts/next-kernel-number

@@ -0,0 +1,20 @@
+#! /bin/bash
+
+max=0
+max_name=""
+
+cd /src/mariux/beeroot/bee-files/
+
+for f in linux-[0-9]*.bee; do
+	[[ $f =~ -([0-9]+).bee ]] || continue
+	if ((  ${BASH_REMATCH[1]} > $max )); then
+		max=${BASH_REMATCH[1]}
+		max_name="$f"
+	fi
+done
+if [ -n "$max_name" ]; then
+	echo $(($max+1))
+else
+	echo "No file linux-[0-9]*.bee found in /src/mariux/beeroot/bee-files/" >&1
+	exit 1
+fi