Auto merge of #37681 - nrc:crate-metadata, r=@alexcrichton

add --crate-type metadata

r? @alexcrichton

diff --cc src/librustc/middle/cstore.rs
Simple merge

diff --cc src/librustc/middle/weak_lang_items.rs
Simple merge

diff --cc src/librustc/session/config.rs
Simple merge

diff --cc src/librustc_driver/driver.rs
Simple merge

diff --cc src/librustc_metadata/creader.rs
Simple merge

diff --cc src/librustc_metadata/cstore.rs
Simple merge

diff --cc src/librustc_metadata/cstore_impl.rs
index 407166203de87b4f12dc263e39a439f21cc6ce5e,cf8240db1958a2936d382cc457a8ce32d944c8dc..ead933384b96d9b4e18bbfbe807270c406e83c02
--- 1/src/librustc_metadata/cstore_impl.rs
--- 2/src/librustc_metadata/cstore_impl.rs
+++ b/src/librustc_metadata/cstore_impl.rs
@@@ -28,11 -28,9 +28,10 @@@ use rustc::mir::Mir
  use rustc::util::nodemap::{NodeSet, DefIdMap};
  use rustc_back::PanicStrategy;
  
- use std::path::PathBuf;
  use syntax::ast;
  use syntax::attr;
 -use syntax::parse::{token, new_parser_from_source_str};
 +use syntax::parse::new_parser_from_source_str;
 +use syntax::symbol::Symbol;
  use syntax_pos::mk_sp;
  use rustc::hir::svh::Svh;
  use rustc_back::target::Target;

diff --cc src/librustc_metadata/decoder.rs
Simple merge

diff --cc src/librustc_metadata/locator.rs
Simple merge

diff --cc src/librustc_trans/back/link.rs
Simple merge

diff --cc src/librustc_trans/base.rs
Simple merge