[viirb] add script to get the firmware

viirb-get-openwrt-firmware.sh

@@ -0,0 +1,14 @@
+#!/bin/sh
+# 2020-10-08, Nico Schottelius
+# See https://ungleich.ch/u/products/viirb-ipv6-box/
+
+if [ $# -ne 1 ]; then
+    echo "$0 openwrt-version"
+    echo "    openwrt-version: for instance 19.07.4"
+    exit 1
+fi
+
+version=$1
+filename=openwrt-${version}-ramips-mt76x8-vocore2-squashfs-sysupgrade.bin
+
+wget -c http://downloads.openwrt.org/releases/${version}/targets/ramips/mt76x8/${filename}