recipes-core: bbappend RAUC system.conf for RPi4

The RAUC package contains the /etc/rauc/system.conf file, which defines
RAUC slot definitions and keyring file, which is used to verify updates.

The bbappend file makes the package machine-specific. For the MACHINE
"raspberrypi4-64" a canned system.conf is provided. For other machines
nothing, yet, happens.

Signed-off-by: Zygmunt Krynicki <zygmunt.krynicki@huawei.com>

meta-ohos-core/recipes-core/rauc/files/raspberrypi4/system.conf

+# SPDX-FileCopyrightText: Huawei Inc.
+#
+# SPDX-License-Identifier: Apache-2.0
+
+[system]
+compatible=ASOS Reference Image for Raspberry Pi 4
+# Use the custom boot loader backend. The handler program is set in the
+# [handlers] section below. This loops in SystemOTA into the update process and
+# delegates slot status and slot active flag responsibilities to it.
+bootloader=custom
+# Keep the RAUC status file in the system data partition, in a directory that
+# is common across revisions of the operating system. In other words, this file
+# is explicitly exempt from the A/B update process. 
+statusfile=/run/mount/sysdata/common/status.raucs
+
+# Description of A/B slots used on the Raspberry Pi 4.
+# Refer to meta-ohos-core/wic/x-raspberrypi.wks.in for details.
+[slot.system.0]
+device=/dev/mmcblk0p2
+bootname=A
+
+[slot.system.1]
+device=/dev/mmcblk0p3
+bootname=B
+
+[keyring]
+# FIXME(zyga): This keyring should be defined somewhere.
+path=/etc/rauc/cert.pem
+
+[handlers]
+# Use SystemOTA for RAUC pre-install and post-install handlers. This is
+# required for correct operation of the custom boot backend as well as for the
+# operation of the state management handlers as provided by SystemOTA. 
+pre-install=/usr/libexec/sysota/rauc-pre-install-handler
+post-install=/usr/libexec/sysota/rauc-post-install-handler
+
+# Use SystemOTA to implement the custom RAUC boot backend. On platforms where
+# RAUC manages the boot loader directly remove this line and set the correct
+# bootloader= in the [system] section.
+bootloader-custom-backend=/usr/libexec/sysota/rauc-custom-boot-handler

meta-ohos-core/recipes-core/rauc/rauc_%.bbappend

+# SPDX-FileCopyrightText: Huawei Inc.
+#
+# SPDX-License-Identifier: Apache-2.0
+
+# For specific MACHINE configurations, provide a pre-baked RAUC system config
+# file. This confi file must be paired with equally tailored SystemOTA config
+# file.
+#
+# FIXME(zyga): The file defines RAUC compatible string which is technically
+# something that SystemOTA should be responsible for (make/model and remodel
+# operations). This should be addressed before re-model is supported.
+FILESEXTRAPATHS_prepend_raspberrypi4-64 := "${THISDIR}/files/raspberrypi4:"
+
+# Make the RAUC package machine-specific. This lets us put the specific configuration
+# file, which encodes the slot configuration, into it safely.
+PACKAGE_ARCH = "${MACHINE_ARCH}"