This issue of separating a build system and a package manager vs lumping it together is a key design decision. We chose to follow Rust's Cargo, which lumps it t

This issue of separating a build system and a package manager vs lumping it together is a key design decision. We chose to follow Rust's Cargo, which lumps it together. It seems like a wrong decision at first (for the reason you stated), but we feel it is actually the right decision: from the user experience it feels much more natural and robust. I was not sure at first, but after playing with Cargo and Rust, you realize that this is the way to go.