Auto merge of #5389 - matklad:one-hard-cs-problem, r=alexcrichton
authorbors <bors@rust-lang.org>
Wed, 18 Apr 2018 15:09:00 +0000 (15:09 +0000)
committerbors <bors@rust-lang.org>
Wed, 18 Apr 2018 15:09:00 +0000 (15:09 +0000)
One hard cs problem

Closes https://github.com/rust-lang/cargo/issues/5313

r? @alexcrichton

Note that, due to the first commit, this still gives us all the benefits of #5249: if RUSTFLAGS is empty, we will run only a single rustc process, even if we can't cache it across different cargo invocations.


Trivial merge