Use UnordSet instead of FxHashSet in define_id_collections!().

compiler/rustc_data_structures/src/fx.rs

@@ -12,7 +12,7 @@ pub type IndexEntry<'a, K, V> = indexmap::map::Entry<'a, K, V>;
 macro_rules! define_id_collections {
     ($map_name:ident, $set_name:ident, $entry_name:ident, $key:ty) => {
         pub type $map_name<T> = $crate::fx::FxHashMap<$key, T>;
-        pub type $set_name = $crate::fx::FxHashSet<$key>;
+        pub type $set_name = $crate::unord::UnordSet<$key>;
         pub type $entry_name<'a, T> = $crate::fx::StdEntry<'a, $key, T>;
     };
 }