Unnecessary recompilation in workspace

I have a client and server and common crate in a workspace, if I build the client, then the server, then the client again, it recompiles all the deps unnecessarily. The verbose output says all the deps are `Fresh`, but they shouldn't be. I think it's an issue with the tarpc code generation causing everything to be marked modified.

My common crate only contains:
```rust
#![feature(plugin)]
#![plugin(tarpc_plugins)]

#[macro_use] extern crate tarpc;

service! {
rpc register(hardware_id: String, version: u32) -> bool;
}
```
And only depends on `tarpc = "0.8.0"` and `tarpc-plugins = "0.1.1"`.

The client and server crates use this crate.
So the code for this should be generated to the same location when server or client builds the common crate, right?

Btw, when I do it this way, I only receive empty strings for `hardware_id` on the server side, why? (`version` arrives correctly.)