Add protobuf to CI

[kathoum]

Add "Protobuf" package set to the CI workflow.

Upgrade the packages:

• protobuf to version 33.4
• abseil to version 20260107.0

Add patch to fix build error in protobuf-c in case there is a DLL in C:\ -- protobuf-c/protobuf-c#778

[danyeaw]

Hey @kathoum and @AlessandroBono - thanks so much for improving this. Since protobuf itself isn't the main focus of Gvsbuild, have you considered adding it to either the existing GTK3 or GTK4 runs rather than adding a completely separate CI run just for it?

We can also change the zip filenames, but it also might be a breaking change for a project if they have some automation around downloading the latest release.

[kathoum]

We don't have preferences about having a separate build rather than adding protobuf to one of the existing runs. The goal is just to make sure that those packages don't break with an update.

I think the difference is mainly for the users who download the release zip (would they prefer more packages in the archive, or rather smaller archives), and maybe for resource usage by github actions. Protobuf is small compared to gtk, so it makes sense to include it, but I'm also planning to add gstreamer (like in #1623) which will be quite large. For this reason @AlessandroBono went for an "Others" bundle, which is a reasonable choice.

In both cases, I don't see a reason for changing the .zip names.

[danyeaw]

Hi @kathoum, I think I would prefer to add this to one of the current CI runs. Would you mind please updating the PR with that?

[kathoum]

Updated the PR to add protobuf to the GTK4 run.

I have also rebased it on the current main and upgraded the versions of abseil and protobuf.