Auto merge of #154861 - mehdiakiki:fix/rlib-digest, r=petrochenkov

Add rlib digest to identify Rust object files



This adds a metadata entry to `rlib` archives that lists which members are Rust object files instead of relying on the filename heuristic in `looks_like_rust_object.file`. I also added a fallback to the old behavior for `rlibs` built by older compilers. 

Part of rust-lang/rust#138243.

Author: bors