Auto merge of #9653 - bjorn3:update_should_use_metadata, r=alexcrichton

Update should_use_metadata function

* Correct the reason for not renaming dylibs
* Add todo for -install-name/-soname usage
* Limit wasm32 executable metadata omission to emscripten. Wasm file don't contain any filename themself.
* Don't omit metadata for executables on macOS. backtrace-rs is now able to load debuginfo for renamed .dSYM files: https://github.com/rust-lang/backtrace-rs/blob/ed3689c2f2b9a31546d75fae389a32a572957dbd/src/symbolize/gimli/macho.rs#L51-L65
* Mention another reason to include the metadata hash for libstd.