[Bug]: `kernel-dtb` does not output when `unset BOOT_FDT_FILE` is present

[EvilOlaf]

What happened?

I noticed this when preparing #8082.
When unset BOOT_FDT_FILE was present there was no output of the preprocessed dts files in output/ folder.
Once commented it worked as expected.

Not sure if this expected or an actual bug.

How to reproduce?

• set unset BOOT_FDT_FILE in board config file.
• use kernel-dtb for the same board and - if applicable - branch
• check output

Haven't tested with other boards/branches though.

Branch

main (main development branch)

On which host OS are you running the build script and observing this problem?

Ubuntu 22.04 Jammy

Are you building on Windows WSL2?

• Yes, my Ubuntu/Debian/OtherOS is running on WSL2

Relevant log URL

https://paste.next.armbian.com/reyawolagi

Code of Conduct

• I agree to follow this project's Code of Conduct

[github-actions]

Jira ticket: AR-2657

[rpardini]

There's no way kernel-dtb can know what to output if that is unset...

[EvilOlaf]

Alright, kind of expected this. As mentioned wasn't sure if it would output something regardless.
Though maybe this should be a fatal error then rather than a warning.

--> (35) WARNING: Board 'orangepi5-max' branch 'edge' [ No BOOT_FDT_FILE set for board, skipping further processing ]