Investigate `mimalloc-rust-sys` dependency not working with latest C standard

[georgefst]

While fixing the Nix shell in #81, we forced use of an older C standard in order to get cargo build working. This is kind of a band-aid fix.

The problematic dependency is mimalloc-rust-sys, which was brought in as a transitive dependency by coln-query, via dbsp. It's unclear why dbsp depends on mimalloc-rust-sys, for which I can't even find a source repo, rather than mimalloc and libmimalloc-sys, which are actively maintained here.

[lstwn]

I came across DBSP's use of mimalloc already while looking into making it compile into WASM.. Good to keep this other issue in mind, thanks!