Rollup merge of #139711 - thaliaarchi:hermit-args, r=jhpratt

Hermit: Unify `std::env::args` with Unix

The only differences between these implementations of `std::env::args` are that Unix uses relaxed ordering, but Hermit uses acquire/release, and Unix truncates `argv` at the first null pointer, but Hermit doesn't. Since Hermit aims for Unix compatibility, unify it with Unix.

The atomic orderings were established in rust-lang/rust#74006 (cc `@euclio)` for Unix and rust-lang/rust#100579 (cc `@joboet)` for Hermit and, before those, they used mutexes and non-atomic statics. I think the difference in orderings is simply from them being changed at different times. The commented explanation for using acquire/release for Hermit is “to broadcast writes by the OS”. I'm not experienced enough with atomics to accurately judge, but I think acquire/release is stronger than needed. Either way, they should match.

Truncating at the first null pointer seems desirable, though I don't know whether it is necessary in practice on Hermit.

cc `@mkroening` `@stlankes` for Hermit

Author: ChrisDenton