Does Cargo always rerun build scripts when it would change an environment variable like OPT_LEVEL? Or is it expected that users need to set e.g. cargo::rerun-if-env-changed=OPT_LEVEL if their scripts make use of it?

It would be helpful to clarify this in the documentation at https://doc.rust-lang.org/cargo/reference/environment-variables.html#environment-variables-cargo-sets-for-build-scripts and/or https://doc.rust-lang.org/cargo/reference/build-scripts.html#rerun-if-env-changed.