Merge branch 'configure-lto' of https://github.com/alexcrichton/rust into rollup

diff --cc src/librustc_trans/back/write.rs
index 39e86bf90fcd910b0fca14fc99bd0c230c9ef8c0,a4af080ebf7e6f7e6d0effc2687e51aa5c9aef4c..db8db16a6c421d6dfd396ac77ddb0c51122f4a18
--- 1/src/librustc_trans/back/write.rs
--- 2/src/librustc_trans/back/write.rs
+++ b/src/librustc_trans/back/write.rs
@@@ -19,8 -18,8 +19,8 @@@ use consts
  use rustc_incremental::{save_trans_partition, in_incr_comp_dir};
  use rustc::dep_graph::{DepGraph, WorkProductFileKind};
  use rustc::middle::cstore::{LinkMeta, EncodedMetadata};
 -use rustc::session::config::{self, OutputFilenames, OutputType, OutputTypes, Passes, SomePasses,
 +use rustc::session::config::{self, OutputFilenames, OutputType, Passes, SomePasses,
-                              AllPasses, Sanitizer};
+                              AllPasses, Sanitizer, Lto};
  use rustc::session::Session;
  use rustc::util::nodemap::FxHashMap;
  use rustc_back::LinkerFlavor;