Auto merge of #4266 - nrc:force, r=alexcrichton
authorbors <bors@rust-lang.org>
Mon, 10 Jul 2017 14:27:19 +0000 (14:27 +0000)
committerbors <bors@rust-lang.org>
Mon, 10 Jul 2017 14:27:19 +0000 (14:27 +0000)
Add a way to force a unit of work to always be rebuilt


Trivial merge