stdarch subtree update Subtree update of `stdarch` to https://github.com/rust-lang/stdarch/commit/5531955678494ee28ec02130a6d94082ad4532da. Created using https://github.com/rust-lang/josh-sync. I saw that there were non-trivial changes made to `std_detect` in `stdarch` recently. So I want to get them merged here before we move forward with https://github.com/rust-lang/rust/pull/143412. r? `@folkertdev`