rust crates in packages

[Nikita Gillmann <nikita%n0.is@localhost>]

Hi,

I am looking at some Rust packages I want to move from wip to pkgsrc
soon, and it seems the way I do it sometimes (all the time?) is not
really disk space friendly. The dependency crates could as well be
thrown into the distfiles dir and not using project subdirs, as they all
come from the same place.

Any objections to this? (and maybe I should start documenting packaging
rust packages eventually, some mk snippets left to be tested)