Remove dylib as a possible value for link.kind

Hello,


`dylib` [seems][1] to be no longer an option for the `kind` key of the `link` attribute.


Regards,
Ivan

[1]: https://github.com/rust-lang/rust/blob/8f8753878644b0bfb38d24781edb9ef2028730f2/src/librustc/metadata/creader.rs#L237