fix compile-fail test for targets without thread locals

Author: mtak-

src/test/compile-fail/issue-43733-2.rs

@@ -5,15 +5,15 @@
 #[cfg(not(target_thread_local))]
 struct Key<T> {
     _data: std::cell::UnsafeCell<Option<T>>,
-    _flag: std::cell::Cell<bool>,
+    _flag: std::cell::Cell<()>,
 }
 
 #[cfg(not(target_thread_local))]
 impl<T> Key<T> {
     const fn new() -> Self {
         Key {
             _data: std::cell::UnsafeCell::new(None),
-            _flag: std::cell::Cell::new(false),
+            _flag: std::cell::Cell::new(()),
         }
     }
 }
@@ -23,7 +23,6 @@ use std::thread::__FastLocalKeyInner as Key;
 
 static __KEY: Key<()> = Key::new();
 //~^ ERROR `std::cell::UnsafeCell<std::option::Option<()>>` cannot be shared between threads
-//~| ERROR `std::cell::Cell<std::thread::local::fast::DtorState>` cannot be shared between threads
-// safely [E0277]
+//~| ERROR cannot be shared between threads safely [E0277]
 
 fn main() {}