openwrt: add snapshot build script

The script downloads all buildinfo and checksums from the OpenWrt
download server and tries to rebuild them. Once done the upstream
checksums are used to verify the newly created files.

Signed-off-by: Paul Spooren <mail@aparcar.org>

bin/reproducible_openwrt_snapshot.sh

+#!/bin/sh
+
+TARGET="${TARGET:-ath79}"
+SUBTARGET="${SUBTARGET:-generic}"
+BASE_DIR="$(pwd)"
+
+# TODO verify stuff
+
+TMP_DIR="$(mktemp -d)"
+
+git clone https://github.com/openwrt/openwrt.git "$TMP_DIR"
+
+pushd "$TMP_DIR"
+
+wget "https://downloads.openwrt.org/snapshots/targets/$TARGET/$SUBTARGET/sha256sums"
+wget "https://downloads.openwrt.org/snapshots/targets/$TARGET/$SUBTARGET/sha256sums.sig"
+wget "https://downloads.openwrt.org/snapshots/targets/$TARGET/$SUBTARGET/config.buildinfo" -O .config
+wget "https://downloads.openwrt.org/snapshots/targets/$TARGET/$SUBTARGET/feeds.buildinfo" -O feeds.conf
+wget "https://downloads.openwrt.org/snapshots/targets/$TARGET/$SUBTARGET/version.buildinfo"
+
+VERSION_COMMIT="$(cat version.buildinfo |  cut -d '-' -f 2)"
+
+git checkout -f "$VERSION_COMMIT"
+
+#./scripts/feeds update -a
+make defconfig
+make -j "$(nproc)"
+
+cp "sha256sums" "./bin/targets/$TARGET/$SUBTARGET/sha256sums"
+
+popd