To build a basic_bootloader that can be combined with another application in the same memory, you need to use a linker script that supports the new memory map.
Building with CMake
If you are building using CMake, then update CMakeLists.txt LINKER_SCRIPT flag to bootloader.ld when compiling a basic_bootloader binary.
set(LINKER_SCRIPT ${MCU_DIR}/bootloader.ld)
Also, make sure to update LINKER_SCRIPT flag to app.ld when compiling an application binary that will be combined with the bootloader binary.
set(LINKER_SCRIPT ${MCU_DIR}/app.ld)
Building with STM32CubeIDE
If you are building using STM32CubeIDE, then there is no need to change the linker script when building a basic_bootloader binary as can be seen below.
But, make sure to change the application linker script from ../../../target/stm32wl55xx_flash.ld to ../../../target/app.ld.
Combining applications
You can combine two binaries such as the basic_bootloader and basic_lorawan by using the bootloader_app_merge python script .
For example:
python bootloader_app_merge.py \
-b ./build/debug/app/basic_bootloader/main.bin \
-a ./build/debug/app/basic_lorawan/main.bin \
-s 1 \
-d 0xB000 \
-c 0xB008 \
-o ./build/debug/app/basic_lorawan/boot_basic_lorawan.bin