odb: Move messages checking to odb to fix deps.

[titan73]

The messages checking was set at db level as odb is an interface and doesn't not have a post-build trigger.
Unfortunately there were no dependencies on other libs besides db such as defin.
So since add_dependencies can only add targets but not files, create a custom target which depends on a generated files which
triggers the call to find_messages.py.

[github-actions]

clang-tidy review says "All clean, LGTM! 👍"

[github-actions]

clang-tidy review says "All clean, LGTM! 👍"

[maliberty]

I assume this is to fix #5687

add_custom_target docs say

The target has no output file and is always considered out of date even if the commands try to create a file with the name of the target. Use the add_custom_command() command to generate a file with dependencies.

I think this should only run when there is a change to a dependency. Can this be accomplished with add_custom_command ?

[github-actions]

clang-tidy review says "All clean, LGTM! 👍"

[titan73]

You're right. PR updated as suggested.
We still need a custom target as add_dependencies accepts only targets.
But this time the custom target depends on a file generated only when the deps have change.

[maliberty]

What is the purpose of the touch command? That file doesn't seem to be referenced.

[titan73]

This file is referenced by add_custom_target(odb_messages DEPENDS messages.txt). This file is in build/src/odb and is only generated when find_messages.py succeeds. This way invoking make will rerun find_messages.py if it's missing (ie find_message.py not run yet) or if a dependencies is changed.
The output of find_messages.py is in src/odb and is always generated whenever find_messages.py succeeds or not which is the current behaviour.

To test the patch I just do a "ls src/odb/messages.txt ../src/odd/messages.txt" from build folder to see how things are going on so I can see if the files are updated and when based on the date. Thins go as intented after testing in the different conditions.

[titan73]

I've renamed the target file to messages_checked to avoid confusion.

[github-actions]

clang-tidy review says "All clean, LGTM! 👍"