avoid unnecessary Thread handle allocation

Author: joboet

library/std/src/sys/unix/locks/queue_rwlock.rs

@@ -210,7 +210,8 @@ impl Node {
     fn prepare(&mut self) {
         // Fall back to creating an unnamed `Thread` handle to allow locking in
         // TLS destructors.
-        self.thread.get_or_init(|| thread_info::current_thread().unwrap_or(Thread::new(None)));
+        self.thread
+            .get_or_init(|| thread_info::current_thread().unwrap_or_else(|| Thread::new(None)));
         self.completed = AtomicBool::new(false);
     }