Only store a LocalDefId in hir::Item.

Items are guaranteed to be HIR owner.

compiler/rustc_metadata/src/native_libs.rs

@@ -53,7 +53,7 @@ impl ItemLikeVisitor<'tcx> for Collector<'tcx> {
                 name: None,
                 kind: NativeLibKind::Unspecified,
                 cfg: None,
-                foreign_module: Some(self.tcx.hir().local_def_id(it.hir_id).to_def_id()),
+                foreign_module: Some(it.def_id.to_def_id()),
                 wasm_import_module: None,
             };
             let mut kind_specified = false;