Add cargo support

[bharrisau]

This is to track the steps towards Cargo now that I've had a change to play with it on a branch.

• Refactor folder layout Move zinc crate source into a subdir #164 Moved all rust code into src #167
• Refactor rake build folder
• Add separate rake tasks to build non-cargo deps (core, rlib)
• Refactor linker scripts, have rake copy selected script to build folder
• Add a zinc config file to specify target
• Develop target spec and cargo.toml files (waiting on Implement flexible target specification rust-lang/rust#16156)
• Deploy external example zinc app

I am wondering why rake is used ? Why not make like other rust projects ?

[farcaller]

why rake is used ?

I like ruby

[bgamari]

@bharrisau what's the status of this? It would be great to get something in this direction merged.

[mcoffin]

Closed by the landing of #285, a cargo based build system.