Auto merge of #3534 - sfackler:opt-level, r=alexcrichton
authorbors <bors@rust-lang.org>
Fri, 13 Jan 2017 18:06:42 +0000 (18:06 +0000)
committerbors <bors@rust-lang.org>
Fri, 13 Jan 2017 18:06:42 +0000 (18:06 +0000)
Allow debuginfo level to be specified

`true` is mapped to `2`, which matches current behavior.

r? @alexcrichton


Trivial merge