Add helper to update uboot

debian/bin/u-boot-install-librem5

+#!/bin/sh
+set -e
+
+dtmodel="/sys/firmware/devicetree/base/model"
+if [ -z "$TARGET" ] && [ -f "${dtmodel}" ]; then
+	case $(cat "${dtmodel}") in
+		"Purism Librem 5 devkit")
+			TARGET="/usr/lib/u-boot/librem5_devkit"
+			;;
+		"Purism Librem 5")
+			TARGET="/usr/lib/u-boot/librem5"
+			;;
+		*)
+			echo >&2 "ERROR: Unknown system: ${dtmodel}"
+			echo >&2 "Specify target: TARGET=/usr/lib/u-boot/UBOOT"
+			exit 1
+			;;
+	esac
+fi
+
+UBOOT_IMAGE=${UBOOT_IMAGE:-"u-boot.imx"}
+
+DEV="$1"
+if [ -z "$DEV" ] || ! shift || [ -n "$*" ]; then
+    echo >&2 "Usage: $0 /dev/your-sd-or-mmc-or-image"
+    exit 1
+fi
+
+if [ ! -w "$DEV" ] && [ -z "$FORCE" ]; then
+    echo >&2 "$0: device/image ($DEV) must be writable"
+    exit 1
+fi
+
+echo "Writing u-boot image"
+dd if=/dev/zero of="$DEV" bs=1024 count=1055 seek=2
+dd if="${TARGET}/${UBOOT_IMAGE}" conv=notrunc of="$DEV" bs=1024 seek=33
+
+sync "$DEV"
+