Godot-specific configurations

[Klaim]

Setup configurations using the flags normally used by Godot projects, see the CMakeLists.txt and/or Scons files in the godot-cpp upstream project.

These configurations should be provided as files to load using config.load.load=<file here> in build2, so that users can build their projects specifically to match the ABI etc. of the Godot project.

Note that this is totally optional as the godot-cpp C api already takes care of differences in ABI etc. but it can be useful to have all the project built the same way if the user wants.

The configuration files should be provided at install or in some other way that is easy to grab/use directly in the user project. The main issue is that to access these configurations, one must first get the project... so not sure how to help with that.

[Klaim]

While working with godot-cpp I realised that the clever hourglass C api makes apparently ABI-stable to use builds from various configurations. The only thing to be wary of is which runtime is used on Windows (debug vs normal/release vs universal).