Revert "rustc_driver: Use the target tools PATH"

This reverts commit e7a71e8.

Author: alexcrichton

src/librustc_driver/driver.rs

@@ -761,8 +761,7 @@ pub fn phase_6_link_output(sess: &Session,
                            trans: &trans::CrateTranslation,
                            outputs: &OutputFilenames) {
     let old_path = env::var_os("PATH").unwrap_or(OsString::new());
-    let mut new_path = sess.target_filesearch(PathKind::All)
-                           .get_tools_search_paths();
+    let mut new_path = sess.host_filesearch(PathKind::All).get_tools_search_paths();
     new_path.extend(env::split_paths(&old_path));
     env::set_var("PATH", &env::join_paths(new_path.iter()).unwrap());