rust_bindgen_library does not allow extra deps

[djmarcin]

Attempting to pass additional deps to rust_bindgen_library fails with Error in rust_library: rule(...) got multiple values for parameter 'deps'. It seems like the libc crate is almost certainly a requirement for nontrivial uses of rust_bindgen_library, so it's not clear how this rule is intended to be used without the ability to pass along additional deps.