Add builds with debugging symbols

[qarmin]

It would be good to see debug builds, to help to find bugs in godot.

[Calinou]

It is possible to add debug builds, but it would take more time to create a new build (I would keep distributing release builds since they perform better).

I should look at using Azure Pipelines to reduce build times, as it allows for up to 10 parallel jobs. I wonder what the per-job time limit is, though.

Edit: As of 2019-03-01, the per-job time limit on Azure Pipelines is 360 minutes, which is sufficient (by far).

[Calinou]

In the meantime, if anyone needs a debug build of a stable release, check out this repository 🙂