Cargo is now distributed together with rustc. Upstream has removed
Cargo.lock from the cargo's repository in cargo 0.23.0, so we can't
build it with locked and freezed dependencies separately anymore.
alexcrichton replied on Feb 1:
> cargo is packaged next to rustc, it's not intended to be a separate
> package but rather built as one unit.
See 5c9665f41c
