GRMLBASE: install extlinux.conf on ARM64

First step in supporting uboot bootloader. Might not work directly
from an ISO though.

Author: zeha

config/media-files/GRMLBASE/boot/extlinux/extlinux.conf

@@ -0,0 +1,32 @@
+default l0
+menu title Grml Live Linux
+prompt 0
+timeout 50
+
+label l0
+menu label Grml Live Linux
+linux /boot/%SHORT_NAME%/vmlinuz
+initrd /boot/%SHORT_NAME%/initrd.img
+fdtdir /boot/%SHORT_NAME%/dtbs/
+append boot=live live-media-path=/live/%GRML_NAME%/ bootid=%BOOTID% \${bootargs}
+
+label l1
+menu label Grml Live Linux: Enable SSH (with random password)
+linux /boot/%SHORT_NAME%/vmlinuz
+initrd /boot/%SHORT_NAME%/initrd.img
+fdtdir /boot/%SHORT_NAME%/dtbs/
+append boot=live live-media-path=/live/%GRML_NAME%/ bootid=%BOOTID% \${bootargs} ssh
+
+label l2
+menu label Grml Live Linux: Load German Keyboard Layout
+linux /boot/%SHORT_NAME%/vmlinuz
+initrd /boot/%SHORT_NAME%/initrd.img
+fdtdir /boot/%SHORT_NAME%/dtbs/
+append boot=live live-media-path=/live/%GRML_NAME%/ bootid=%BOOTID% \${bootargs} lang=de
+
+label l3
+menu label Grml Live Linux: Debug Mode
+linux /boot/%SHORT_NAME%/vmlinuz
+initrd /boot/%SHORT_NAME%/initrd.img
+fdtdir /boot/%SHORT_NAME%/dtbs/
+append boot=live live-media-path=/live/%GRML_NAME%/ bootid=%BOOTID% \${bootargs} initcall verbose debug=vc systemd.log_level=debug systemd.log_target=kmsg log_buf_len=1M

config/media-scripts/GRMLBASE/32-uboot

@@ -0,0 +1,25 @@
+#!/bin/bash
+# Filename:      ${GRML_FAI_CONFIG}/media-scripts/GRMLBASE/32-uboot
+# Purpose:       Install u-boot configuration
+# Authors:       grml-team (grml.org)
+# Bug-Reports:   see http://grml.org/bugs/
+# License:       This file is licensed under the GPL v2 or any later version.
+################################################################################
+
+set -u
+set -e
+
+if ! ifclass ARM64 ; then
+  exit 0
+fi
+
+# FAI sets $target, but shellcheck does not know that.
+target=${target:?}
+# shellcheck source=/dev/null
+. "$GRML_LIVE_CONFIG"
+
+media_dir="${target}/${GRML_LIVE_MEDIADIR}"
+
+grml-live-command copy-media-files media -r /boot/extlinux
+
+grml-live-adjust-boot-files "${media_dir}"/boot/extlinux/extlinux.conf