Auto merge of #4065 - michaelwoerister:smarter-cargo-incremental, r=alexcrichton
authorbors <bors@rust-lang.org>
Wed, 17 May 2017 13:54:21 +0000 (13:54 +0000)
committerbors <bors@rust-lang.org>
Wed, 17 May 2017 13:54:21 +0000 (13:54 +0000)
Only compile user-modifiable projects incrementally.

Fixes #3972. Thanks for pointing me to the correct implementation, Alex!

r? @alexcrichton


Trivial merge