Reuse snapshot LLVM by default instead of rebuilding

[brson]

For the most common use cases, it is not strictly necessary to rebuild LLVM. This will be very helpful for new users as well as for the servo bots.

[catamorphism]

Nominating for milestone 5, production-ready

[graydon]

probably LLVM will be on its own package,

[graydon]

accepted for production-ready milestone

[pnkfelix]

visited for bug triage from 2013-07-22.

Is this bug talking about hosting snapshots of the patched LLVM builds alongside our snapshots of rustc? Or is it talking about getting the snapshot from somewhere else after we have pushed our LLVM patches upstream?

(I am assuming the former, since I suspect we'd be okay with hosting LLVM snapshots and do not want to give up the flexibility of patching LLVM when necessary.)

[huonw]

Triage: still an issue.

[sanxiyn]

Since #10809, snapshot is statically linked and there is no "snapshot LLVM" per se. What is the plan on this now?

[brson]

I think this is probably irrelevant. Building LLVM is pretty fast lately since we stopped building so many components and with #9876 we'll provide binary nightly installers for users.

[pnkfelix]

The main client who would benefit from this are new users, who would be better served by #9876.

So, closing in favor of #9876.