Auto merge of #24437 - fhahn:issue-24434, r=alexcrichton

closes #24434 

This PR changes executes `syntax::config::strip_unconfigured_items` before `syntax::feature_gate::check_crate_macros(sess.codemap()`. As far as I know, `strip_unconfigured_items` should be independent of `check_crate_macros`.

src/test/run-pass/issue-24434.rs

@@ -0,0 +1,16 @@
+// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// compile-flags:--cfg set1
+
+#![cfg_attr(set1, feature(custom_attribute))]
+
+#![foobar]
+fn main() {}