Starting from auto-generated code isn't considered a proper bootstrap process by the Bootstrappable Builds project. You need to be able to start without any binaries or auto-generated code from the project itself. Usually that would mean starting with a basic implementation in another language, but starting with an older version of the same project that was written in another language and then going through several older versions of different milestones is often easier than reimplementing the language from scratch in another language.

https://bootstrappable.org/