Auto merge of #43092 - aidanhs:aphs-retry-llvm-tarball, r=alexcrichton
Auto merge of #43092 - aidanhs:aphs-retry-llvm-tarball, r=alexcrichton

Retry downloading llvm commit tarball

As promised on https://github.com/rust-lang/rust/pull/42816#issuecomment-312890169

r? @alexcrichton

GBGamer/rust,aidancully/rust,aidancully/rust,graydon/rust,aidancully/rust,GBGamer/rust,aidancully/rust,graydon/rust,GBGamer/rust,graydon/rust,GBGamer/rust,GBGamer/rust,graydon/rust,graydon/rust,GBGamer/rust,aidancully/rust,GBGamer/rust,aidancully/rust,GBGamer/rust,graydon/rust