cmake: allow shield overlays in APPLICATION_CONFIG_DIR

[kartben]

Add support for shield-specific overlays (including suffix support). They are searched in the 'boards/shields' directory of the application configuration directory.

Fixes #86592

Still need to add some docs, and possibly some tests as well.

poke @JordanYates

[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

[github-actions]

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[lromeraj]

@kartben This looks like a very useful addition. Are you still working on it?

[kartben]

@kartben This looks like a very useful addition. Are you still working on it?

mmm kind of dropped the ball :| I guess this could get in with docs added in a second stage, but the documentation maintainer in me will pretend I just didn't say that :)

[lromeraj]

@kartben Looking at the code, I believe this could support both .overlay and .conf extensions (not just .overlay). This would allow attaching configuration files to specific overlays, so the application can configure “addons” simply by using the shields folder—which I think is quite useful. Many times I’ve had to implement this logic manually in the application’s CMakeLists.txt.

For example:

# ...

set(shield_conf_path ${shields_dir}/${shield_name}.conf)
set(shield_overlay_path ${shields_dir}/${shield_name}.overlay)

if(EXISTS ${shield_overlay_path})
  list(APPEND DTC_OVERLAY_FILE ${shield_overlay_path})
endif()

if(EXISTS ${shield_conf_path})
  list(APPEND OVERLAY_CONFIG ${shield_conf_path})
endif()

# ...

Also, the documentation should clarify that the shield list needs to be passed as -DSHIELD_AS_LIST= instead of using the --shield flag.

[github-actions]

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