If you're producing a library that you intend to be used from C (or another
language through a C FFI), there's no need for Rust to include Rust-specific
stuff in the final object code. For libraries like that, you'll want to use
cdylib crate type in your
[lib] crate-type = ["cdylib"]
This will produce a smaller binary, with no Rust-specific information inside of it.