Change crate type to cdylib

[baby-bell]

Cdylib was added to Cargo in 1.11, and since it strips the rust metadata, is the preferred way of doing FFI.

[ustulation]

@baby-bell 👍 Yes - it caused a ~25% reduction in size of .so in my project. Do you know if there is any reason why/when we should use dylib or is that going to be deprecated ?

[shepmaster]

Yes, this is something I was hoping to get around to, thank you for the reminder!

More than just switching it, I'd like to add a section containing the why and the differences (touching on some of what @ustulation is asking).

[baby-bell]

@ustulation I don't think dylib is going to be deprecated any time soon, but its use case is limited (it's really only useful for internal Rust stuff). For almost all purposes, cdylib is the way to go, especially since it allows LTO among other nice things.

[shepmaster]

Indeed, there was one tricky aspect to cdylibs.