Fir now compiles to C (+ extensible named types, associated types, modules, and more)

One of my original goals with Fir was to bootstrap it as early as possible. I was so determined, I committed the first code for the self-hosted compiler in the 322nd commit, on 11 April 2025, after less than a year of development in the open source1, when it was barely usable. To understand how early this is, we’re currently on commit 1,052, and in my opinion it only recently became somewhat usable. Unsurprisingly, this turned out to be a challenge, and I had to accept the fact that a compiler for a non-trivial language is a lot of work. You really need a lot of language features + a good implementation (generating fast code) for it. It’s not that it cannot be done otherwise, but the process becomes extremely slow, tedious, and boring. Something else that became evident as I worked on the self-hosted compiler was that, even if I finish it with just the features we have, I’ll have to refactor it quite significantly as we implement the planned features, to the point where it could feel…