Spurious multiple crate version warning when using --extern

[bkoropoff]

Test Case

lib.rs

#![crate_name = "bar"]
#![crate_type = "rlib"]

test.rs

#![feature(phase)]

#[phase(plugin, link)]
extern crate foo;

fn main() {
}

Build

$ rustc lib.rs
$ rustc test.rs --extern foo=./libbar.rlib

Output

warning: using multiple versions of crate `bar`
test.rs:4:1: 4:18 note: used here
test.rs:4 extern crate foo;
          ^~~~~~~~~~~~~~~~~
note: crate name: bar
test.rs:4:1: 4:18 note: used here
test.rs:4 extern crate foo;
          ^~~~~~~~~~~~~~~~~
note: crate name: bar

Analysis

Use of #[phase(plugin, link)] causes the crate to be resolved twice. Looking at debug output, a bug is causing the two resolutions to load the same crate twice with separate cnums. I believe I have identified a fix and will be submitting a PR shortly.