Function find_bundled_library 

fn find_bundled_library(
    lib: &NativeLib,
    sess: &Session,
    crate_types: &[CrateType],
) -> Option<Symbol>

If lib is a static library that is bundled into the rlib as a packed archive, returns the file name of that archive. Returns None for libraries that are instead unpacked into loose object files, or not bundled at all.