MSRV 1.77.0 TODO

[asomers]

Whenever raising the MSRV to 1.77.0 for any reason, we should:
[ ] Use Mutex::clear_poison always, regardless of the nightly feature.
https://blog.rust-lang.org/2024/03/21/Rust-1.77.0.html
[ ] Revert the lint suppression in #574 and instead add something like this to mockall/build.rs:

println!("cargo::rustc-check-cfg=cfg(target_os, values(\"multics\"))");