Make buildroot a git submodule

have

@@ -0,0 +1,11 @@
+#!/bin/sh
+
+case "$1" in
+    fun)
+	buildroot/utils/brmake -C buildroot BR2_EXTERNAL=../FunKey O=../FunKey/output
+	;;
+    *)
+	echo "You can only have fun!" >&2
+	exit 1
+	;;
+esac