Sudden 99% + Build Time Improvement Going from 1.66.1 to 1.71.0

Not trying to look a gift horse in the mouth or anything, but wtf.

My project using axum and bb8-tokio-postgres was compiling slow as hell, 44.2s for an incremental change, so I started looking into ways to improve it. Very little time was being spent on actual codegen so I was at a loss. But switching over to the nightly channel saw my cold build go from 207s to 76s, and a hot build go from 44.2s to .3s.

Again, cool, and everything seems to be working, but what was even going on there?