Support rpi3 and rpi 4 boards

Due to rpi3 not supporting GPT disks, we need to separate the building
into rpi3 and 4 so rpi4 gets GPT disks and can auto-expand the last
partition properly (and add extra partitions and so on)

This also includes some cleanup for the luet cache dirs, includes the
kairos-agent which was missing from the image for pulling images, and
cleans up the lvm vgs if they were left

Signed-off-by: Itxaka <itxaka@kairos.io>

tools-image/arm/boards/rpi4.sh

@@ -0,0 +1,22 @@
+#!/bin/bash
+
+partprobe
+
+kpartx -va $DRIVE
+
+image=$1
+
+if [ -z "$image" ]; then
+    echo "No image specified"
+    exit 1
+fi
+
+set -ax
+TEMPDIR="$(mktemp -d)"
+echo $TEMPDIR
+mount "${device}p1" "${TEMPDIR}"
+
+# Copy all rpi files
+cp -rfv /rpi/* $TEMPDIR
+
+umount "${TEMPDIR}"