Add flash.sh

This simple script helps automate the process of flashing Fedora CoreOS
onto a SD card for a Raspberry Pi.

flash.sh

@@ -0,0 +1,35 @@
+#!/bin/sh
+# vim: set sw=4 ts=4 sts=4 et :
+
+set -eu
+
+ignition=${1}
+dev=${2:-/dev/disk/by-id/usb-Generic_STORAGE_DEVICE_000000001206-0:0}
+
+if [ -z "${ignition}" ]; then
+    printf 'usage: %s ignition\n' "${0##*/}" >&2
+    exit 2
+fi
+
+if [ $(id -u) -ne 0 ]; then
+    sudo=sudo
+fi
+
+${sudo} coreos-installer install \
+    -a aarch64 \
+    -s stable \
+    -i "${ignition}" \
+    --console ttyS0,115200n8 \
+    "${dev}"
+sync; sync; sync
+
+until [ -n "${efi_part}" ]; do
+    efi_part=$(
+        lsblk -o LABEL,PATH \
+        | awk '$1=="EFI-SYSTEM"{print $2}'
+    )
+done
+pmount "${efi_part}" coreos-efi
+rsync -ah --ignore-existing RPi4boot/boot/efi/ /media/coreos-efi/
+sync; sync; sync
+pumount coreos-efi