Honor current target when checking conditional compilation values

This is fixed by simply using the currently registered target in the
current session. We need to use it because of target json that are not
by design included in the rustc list of targets.

compiler/rustc_interface/src/util.rs

@@ -110,7 +110,7 @@ pub fn create_session(
     add_configuration(&mut cfg, &mut sess, &*codegen_backend);
 
     let mut check_cfg = config::to_crate_check_config(check_cfg);
-    check_cfg.fill_well_known();
+    check_cfg.fill_well_known(&sess.target);
 
     sess.parse_sess.config = cfg;
     sess.parse_sess.check_config = check_cfg;