Emery is a simple glue layer between Ruby and Rust. Its goal is to allow the creation of Rust based Ruby extensions and allow idomatic code on both sides of the interface.
Ruby will only look at certain file extensions for compiled extensions. This is limited to .bundle on Mac, but rust will only compile to .dylib. To fix you need to relink your created dylibs to create bundles, eg:
ld target/debug/examples/libyourlib.dylib -bundle -arch x86_64 -platform_version macos 12.0 12.0 -o yourlib.bundle