I thought about that. The big benefit of using `const` here is that I can lean on my existing abstractions (e.g. Bitboard, Square, Direction) which I was already using in the engine. In order to use those abstractions in `build.rs`, I would have to split out those base data structures into a separate crate. I found empirically that splitting out code into a separate crate resulted in an observable Elo reduction (though this was about a year ago, so I forget how much), even with `lto=true`.