scripts: west_commands: build: Remove build warning

[FelixWang47831]

For non-pristine build, there is warning, which is unnecessary. For example:

If I have run "west build -b frdm_ke17z ./samples/hello_world -p " before, after make some code changes, I want to run a non-pristine build:
(.venv) ➜ zephyr git:(main) ✗ west build
WARNING: This looks like a fresh build and BOARD is unknown; so it probably won't work. To fix, use --board=.
Note: to silence the above message, run 'west config build.board_warn false'
ninja: no work to do.

It's not a fresh build and the "board" variable can be got from CMake Cache.
This patch is trying to get board after cmake cache is got by "self._update_cache()".

This is a regression introduced by #94231

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[carlescufi]

I tried reproducing this but could not. What kind of changes did you make between:
west build -b frdm_ke17z ./samples/hello_world -p
and
west build

so that you got that warning? for me it works just fine if I just change .c files

[FelixWang47831]

Hi @carlescufi Actually I have encountered this warning even without any code changes.

Have you run "west config build.board_warn false" before?

[carlescufi]

Have you run "west config build.board_warn false" before?

Something is off here, because:

❯ west build -b frdm_ke17z ./samples/hello_world -p
[builds]

❯ west config build.board_warn
true

❯ west build
ninja: no work to do.

I cannot reproduce your issue at all. @pdgendt can you reproduce it?

[henrikbrixandersen]

I cannot reproduce your issue at all. @pdgendt can you reproduce it?

I can reproduce it here.

[pdgendt]

I cannot reproduce your issue at all. @pdgendt can you reproduce it?

I can reproduce it here.

Yes, me too

[pdgendt]

I cannot reproduce your issue at all. @pdgendt can you reproduce it?

Do you have a board configured with

$ west config build.board

[pdgendt]

CC @nordic-krch

$ git bisect bad
5718af02c522c195f24951d5e439b9638250a0f5 is the first bad commit
commit 5718af02c522c195f24951d5e439b9638250a0f5
Author: Krzysztof Chruściński <[email protected]>
Date:   Thu Aug 7 16:39:31 2025 +0200

    scripts: west_command: build: Support for conditional platform configs

    extra_configs or extra_args can use additional filtering which was not
    supported by the west build command. West is not aware of arch so that
    filter type is not supported but platform (board) is known so it can
    be used to apply expected configuration.

    Signed-off-by: Krzysztof Chruściński <[email protected]>

 scripts/west_commands/build.py | 46 ++++++++++++++++++++++++++++--------------
 1 file changed, 31 insertions(+), 15 deletions(-)

[nordic-krch]

Thanks for fixing that. It was me, moving board finding to the earlier stage.

[carlescufi]

The reason that I wasn't seeing the warning is that I had board.build defined in my config, which then provided a board for every build.

[pdgendt]

Thanks for fixing that. It was me, moving board finding to the earlier stage.

@nordic-krch I'm actually looking back to your change, with what you introduced the board can get a different value based on if the cache is updated or not.
Maybe the solution is to move the following up in the function instead?

zephyr/scripts/west_commands/build.py

Lines 271 to 272 in 6c1b1dc

	self._sanity_check()
	self._update_cache()

EDIT: Adding DNM for now

[FelixWang47831]

This issue will be fixed by #95383. Hence close this PR.