build openwrt with thistle support

build-owrt-thistle.sh

# fetch imagebuilder tooling
$ wget https://downloads.openwrt.org/releases/22.03.2/targets/ipq40xx/generic/openwrt-imagebuilder-22.03.2-ipq40xx-generic.Linux-x86_64.tar.xz
$ tar -xf openwrt-imagebuilder-22.03.2-ipq40xx-generic.Linux-x86_64.tar.xz
$ cd openwrt-imagebuilder-22.03.2-ipq40xx-generic.Linux-x86_64

# add tuc binary to image
$ mkdir -p localfs/usr/bin
$ cd localfs/usr/bin
$ wget -O tuc https://downloads.thistle.tech/embedded-client/0.1.6/tuc-armv7-unknown-linux-musleabihf
$ chmod +x tuc

# copy thisle config to device, assuming assets are in ~/thistle
$ cd ../..
$ mkdir -p etc/config
$ cd etc/config
$ cp ~/thistle/currently_booted.sh
$ cp ~/thistle/switch_bootpart.sh .
$ cp ~/thistle/config.json .

# rebuild image
$ cd ../../..
$ make image PROFILE="linksys_mr8300" PACKAGES="lsblk" FILES="files"

# built artifact in bin/targets/ipq40xx/generic
$ ls bin/targets/ipq40xx/generic/openwrt-22.03.2-ipq40xx-generic-linksys_mr8300-squashfs-factory.bin