Normalize main return type during mono item collection & codegen

Author: tmiasko

src/main_shim.rs

@@ -51,7 +51,10 @@ pub(crate) fn maybe_create_entry_wrapper(
         // late-bound regions, since late-bound
         // regions must appear in the argument
         // listing.
-        let main_ret_ty = tcx.erase_regions(main_ret_ty.no_bound_vars().unwrap());
+        let main_ret_ty = tcx.normalize_erasing_regions(
+            ty::ParamEnv::reveal_all(),
+            main_ret_ty.no_bound_vars().unwrap(),
+        );
 
         let cmain_sig = Signature {
             params: vec![