Auto merge of #1522 - alexcrichton:issue-1512, r=huonw
authorbors <bors@rust-lang.org>
Tue, 14 Apr 2015 02:19:39 +0000 (02:19 +0000)
committerbors <bors@rust-lang.org>
Tue, 14 Apr 2015 02:19:39 +0000 (02:19 +0000)
They weren't rlibs so they were left out, but targets which have `plugin = true`
should be passed in to `--extern` regardless.

Closes #1512


Trivial merge