Fix Compositor concurrent initialization

It seems that initializing the compositor in a
different thread can cause issues in some environments.

futures/src/backend/native/thread_pool.rs

@@ -11,6 +11,10 @@ impl crate::Executor for Executor {
     fn spawn(&self, future: impl Future<Output = ()> + Send + 'static) {
         self.spawn_ok(future);
     }
+
+    fn block_on<T>(&self, future: impl Future<Output = T>) -> T {
+        futures::executor::block_on(future)
+    }
 }
 
 pub mod time {