For instance, if you are building export templates for Godot 3.1.1, version.txt should contain 3.1.1.stable on the first line (and nothing else). This version identifier is based on the major, minor, patch (if present) and status lines of the version.py file in the Godot Git repository. If you are developing for multiple platforms, macOS is definitely the most convenient host platform for cross-compilation, since you can cross-compile for almost every target (except for UWP).