Bluetooth: Mesh: Add sysbuild support to Light DFU overlay

This does the following:

 * Add sysbuild_dfu.conf to enable the bootloader when building with DFU
   support.
 * Replace overlay-dfu.conf with prj_dfu.conf, to enable use of
   FILE_SUFFIX to specify all required config for the DFU configuration

Signed-off-by: Ludvig Jordet <ludvig.jordet@nordicsemi.no>

samples/bluetooth/mesh/light/prj_dfu.conf

@@ -0,0 +1,72 @@
+#
+# Copyright (c) 2024 Nordic Semiconductor ASA
+#
+# SPDX-License-Identifier: LicenseRef-Nordic-5-Clause
+#
+CONFIG_NCS_SAMPLES_DEFAULTS=y
+
+# Deffered logging helps improve LPN power consumption
+# when friendship is established.
+CONFIG_LOG_MODE_DEFERRED=y
+
+# General configuration
+CONFIG_SYSTEM_WORKQUEUE_STACK_SIZE=2048
+CONFIG_FLASH=y
+CONFIG_FLASH_MAP=y
+CONFIG_NVS=y
+CONFIG_SETTINGS=y
+CONFIG_NVS_LOOKUP_CACHE=y
+CONFIG_SETTINGS_NVS_NAME_CACHE=y
+CONFIG_HWINFO=y
+CONFIG_DK_LIBRARY=y
+CONFIG_PM_SINGLE_IMAGE=y
+CONFIG_PM_PARTITION_SIZE_SETTINGS_STORAGE=0x8000
+CONFIG_SOC_FLASH_NRF_PARTIAL_ERASE=y
+
+# Bluetooth configuration
+CONFIG_BT=y
+CONFIG_BT_DEVICE_NAME="New Mesh Light"
+CONFIG_BT_L2CAP_TX_BUF_COUNT=8
+
+CONFIG_BT_OBSERVER=y
+CONFIG_BT_PERIPHERAL=y
+CONFIG_BT_SETTINGS=y
+# Increase RX stack size to avoid overflow during provisioning
+CONFIG_BT_RX_STACK_SIZE=2700
+
+# Disable unused Bluetooth features
+CONFIG_BT_CTLR_LE_ENC=n
+CONFIG_BT_PHY_UPDATE=n
+CONFIG_BT_CTLR_CHAN_SEL_2=n
+CONFIG_BT_CTLR_MIN_USED_CHAN=n
+CONFIG_BT_CTLR_PRIVACY=n
+
+# Bluetooth Mesh configuration
+CONFIG_BT_MESH=y
+CONFIG_BT_MESH_RELAY=y
+CONFIG_BT_MESH_FRIEND=y
+CONFIG_BT_MESH_TX_SEG_MAX=10
+CONFIG_BT_MESH_PB_GATT=y
+CONFIG_BT_MESH_GATT_PROXY=y
+CONFIG_BT_MESH_PROXY_USE_DEVICE_NAME=y
+CONFIG_BT_MESH_DK_PROV=y
+
+# Bluetooth Mesh models
+CONFIG_BT_MESH_ONOFF_SRV=y
+
+# ==== DFU specific configuration ====
+
+# Enable point to point DFU over SMP
+CONFIG_BOOTLOADER_MCUBOOT=y
+CONFIG_NCS_SAMPLE_MCUMGR_BT_OTA_DFU=y
+CONFIG_NCS_SAMPLE_MCUMGR_BT_OTA_DFU_SPEEDUP=y
+
+# Enable Extended Advertiser to advertise BT SMP service
+CONFIG_BT_EXT_ADV=y
+CONFIG_BT_EXT_ADV_MAX_ADV_SET=6
+
+# One extra connection for mesh GATT/proxy and one for SMP BT.
+CONFIG_BT_MAX_CONN=3
+
+# One extra identity for SMP service
+CONFIG_BT_ID_MAX=2

samples/bluetooth/mesh/light/sample.yaml

@@ -26,5 +26,5 @@ tests:
       - nrf21540dk/nrf52840
       - nrf54l15pdk/nrf54l15/cpuapp
     platform_allow: nrf52840dk/nrf52840 nrf21540dk/nrf52840 nrf54l15pdk/nrf54l15/cpuapp
-    extra_args: OVERLAY_CONFIG=overlay-dfu.conf
+    extra_args: FILE_SUFFIX=dfu
     tags: bluetooth ci_build sysbuild

samples/bluetooth/mesh/light/sysbuild_dfu.conf

@@ -0,0 +1,7 @@
+#
+# Copyright (c) 2024 Nordic Semiconductor
+#
+# SPDX-License-Identifier: LicenseRef-Nordic-5-Clause
+#
+
+SB_CONFIG_BOOTLOADER_MCUBOOT=y