Update landoscript merge_day.py to accomodate Thunderbird

[dandarnell]

Thunderbird does not have a CLOBBER file, so this PR bypasses that requirement for the merge_day action when run on Thunderbird repos.

[bhearsum]

Let's make this cleaner and more explicit by making clobber file operations configurable at the payload level rather than hardcoding this magic string in this action. I expect we could add something like update_clobber_file to MergeInfo that defaults to true (to preserve existing behaviour) and override it in your task configuration.

If you need any additional pointers here just let me know.

[dandarnell]

Let's make this cleaner and more explicit by making clobber file operations configurable at the payload level rather than hardcoding this magic string in this action. I expect we could add something like update_clobber_file to MergeInfo that defaults to true (to preserve existing behaviour) and override it in your task configuration.

If you need any additional pointers here just let me know.

Good point. I've updated the patch to update the CLOBBER file based on update_clobber_file in MergeInfo, which defaults to true.

[bhearsum]

The merge_day_payload part of the schema should get updated for this. (In fact, I think you'll end up with a MALFORMED_PAYLOAD if you try to set this without updating it.)

If you want to give this a run through on try feel free to stop by #firefox-ci on Matrix and have someone push it to the dev workers.

I also suggest you add a test to cover this behaviour, but seeing as it's a Thunderbird-specific path I'll leave that up to you and not block on it.