Establish Infrastructure

[makai410]

• devtool: A helper for maintaining rustc_public. The main logic for commands like build is implemented here. This PR implements ./x build, ./x test [--bless], ./x fmt [--check], ./x githook and ./x clean. Windows is not supported yet.
• This PR turns the compiletest crate into a single file, making it possilbe to run test suites using cargo test.

[celinval]

Amazing! On the file structure, since this repo is also meant to store files related to the project, can I suggest that we create a rustc_public folder with the code relevant for the crate. Or would that mess up with the josh-sync?

[celinval]

I was also wondering if you could break down the PR a bit more. I think there are changes here that are ready to be merged independently

[makai410]

Amazing! On the file structure, since this repo is also meant to store files related to the project, can I suggest that we create a rustc_public folder with the code relevant for the crate. Or would that mess up with the josh-sync?

It seems feasible by writing a filter to the josh, though I haven't tried it yet. IMO it's OK to keep our rustc_public code in the src/ folder, and miri does the same.

I was also wondering if you could break down the PR a bit more. I think there are changes here that are ready to be merged independently

Yea makes sense. I'll split it up.