0.69 introduces issue with constantly rebuilding

As the title suggests, I've bisected 0.69 as introducing an issue where bindgen is constantly rebuilt during the build process. Or maybe the code that bindgen generates. This was found in the gdext project https://github.com/godot-rust/gdext. This project generates bindings for rust and the godot game engine.

We don't have a simple mrp. But if you clone gdext, update bindgen to 0.69 or later, and follow the book's hello world guide, you should be able to reproduce this issue: https://godot-rust.github.io/book/index.html

Note: This was discovered on PopOS 22.04 (an Ubuntu derivative). I have not tested this on any other OS's. If you have any questions, please @me.

@Bromeon is the maintainer of gdext and may also be able to provide additional details if needed.

Edit:

I just realizied @me is an actual handle. Sorry about that 😅 @TCROC is my handle :)

Clone the gdext project, update bindgen to 0.69 or later, and follow the book's hello-world guide to reproduce the repeated rebuild. Compare the build behavior before and after the bindgen update, then identify and document the cause of the constant rebuilding.