Fix NRF flashbundle (#15262)

The flashbundle is using the zephyr.hex which doesn't boot if a bootloader
is DFU  is enabled, instead use merged.hex when it is generated.

config/nrfconnect/app/copy-flashbundle-firmware.cmake

@@ -0,0 +1,25 @@
+#
+#   Copyright (c) 2022 Project CHIP Authors
+#
+#   Licensed under the Apache License, Version 2.0 (the "License");
+#   you may not use this file except in compliance with the License.
+#   You may obtain a copy of the License at
+#
+#       http://www.apache.org/licenses/LICENSE-2.0
+#
+#   Unless required by applicable law or agreed to in writing, software
+#   distributed under the License is distributed on an "AS IS" BASIS,
+#   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+#   See the License for the specific language governing permissions and
+#   limitations under the License.
+#
+
+# Copy the merged.hex file if it exists, otherwise copy zephyr.hex
+
+set(HEX_NAME merged.hex)
+
+if(EXISTS "zephyr/${HEX_NAME}")
+  configure_file("zephyr/${HEX_NAME}" "${FLASHBUNDLE_FIRMWARE}" COPYONLY)
+else()
+  configure_file("zephyr/${KERNEL_HEX_NAME}" "${FLASHBUNDLE_FIRMWARE}" COPYONLY)
+endif()

config/nrfconnect/app/flashing.cmake

@@ -41,7 +41,7 @@ add_custom_command(OUTPUT "${FLASHBUNDLE_FLASHER_PLATFORM}"
 
 add_custom_command(OUTPUT "${FLASHBUNDLE_FIRMWARE}"
     DEPENDS zephyr/${KERNEL_HEX_NAME}
-    COMMAND ${CMAKE_COMMAND} ARGS -E copy "zephyr/${KERNEL_HEX_NAME}" "${FLASHBUNDLE_FIRMWARE}"
+    COMMAND ${CMAKE_COMMAND} ARGS -DFLASHBUNDLE_FIRMWARE=${FLASHBUNDLE_FIRMWARE} -DKERNEL_HEX_NAME=${KERNEL_HEX_NAME} -P "${CHIP_ROOT}/config/nrfconnect/app/copy-flashbundle-firmware.cmake"
     VERBATIM)
 
 add_custom_command(OUTPUT "${CMAKE_PROJECT_NAME}/${CMAKE_PROJECT_NAME}.flash.py"