Looks like our pinned test/flake.lock was being ignored and the latest
version of all inputs was being used. This should fix that oversight
(and give us better caching to boot)
We don't need to nest `cleanCargoSource` and `path` just to populate a
default value for `name`. As they both ultimately delegate to
`builtins.path`, the nesting can lead to IFD in situations which are
otherwise avoidable
