Auto merge of #3693 - alexcrichton:improve, r=alexcrichton
authorbors <bors@rust-lang.org>
Mon, 13 Feb 2017 18:48:08 +0000 (18:48 +0000)
committerbors <bors@rust-lang.org>
Mon, 13 Feb 2017 18:48:08 +0000 (18:48 +0000)
Rework some required-features tests

Don't delete the build dir as this ends up being flaky on Windows.


Trivial merge