CONFIG_BOOTLOADER_MCUBOOT not working on ncs.2.7..0

[Ars Morozov]

Hello, we have application based on ncs v2.7.0. We use cmakepreset and cmake for building application. We want to add DFU functionality to our project. 
We study following docs:
https://docs.nordicsemi.com/bundle/ncs-latest/page/mcuboot/readme-ncs.html which describe how to add bootloader functionality and also handle multi-image build (boot+app).

But it seems that this article is not actual because now we must use Zephyr's sysbuild as it decribed here - https://docs.nordicsemi.com/bundle/ncs-latest/page/nrf/releases_and_maturity/migration/migration_sysbuild.html, Or not?

Anyway we tried to add CONFIG_BOOTLOADER_MCUBOOT definition in prj.conf and build failed when it builds bootloader and show errors when building extra modules of our application (why it build extra modules of application?). When attempt without CONFIG_BOOTLOADER_MCUBOOT it builds successfully.

PS: We can't donwgrade to ncs 2.6.xx because we need GNSS subsystem which was added in 2.7.xx 

[Udi Vahaba]

You need to add sysbuild.conf file to your project parent folder

./YOUR_APP
├── prj.conf
├── CMakeLists.txt
├── src
│   └── main.c
└── sysbuild.conf

In the sysbuild.conf file you need to add - SB_CONFIG_BOOTLOADER_MCUBOOT=y

That should fix your problem.