Make a special base game output to build CDDA game from source as a fallback

[cloudyluna]

Their Linux executables were deleted for some reason for the currently pinned version. Not sure, why.

Originally posted by @cloudyluna in #14 (comment)

Since CDDA release managers could delete, add, or modify existing release artifacts even after release, I think it's better to serve a "build from source" output as an alternative.

Furthermore, I think it's great for reproducibility in case things happen upstream.