Auto merge of #4638 - efyang:docs-cc, r=alexcrichton
authorbors <bors@rust-lang.org>
Wed, 18 Oct 2017 14:04:33 +0000 (14:04 +0000)
committerbors <bors@rust-lang.org>
Wed, 18 Oct 2017 14:04:33 +0000 (14:04 +0000)
Update docs to use cc instead of gcc

Closes #4626.


Trivial merge