making revision number for parsing of godot version optional

[thinkrapido]

this might help for custom_builds without revision number like the one of nixpkgs.godot_4

[Bromeon]

The codegen (and CI) currently rely on the Godot version being either:

• a stable release with a version number
• a custom build with a Git revision number

Does your use case not fall into any of those? Why not, and how does it look?

[Bromeon]

@thinkrapido Any update? Without a clearly described use case, I would close this.