Ignore oneshot::send_before_recv_timeout

Author: JonathanBrouwer

library/std/tests/sync/oneshot.rs

@@ -84,6 +84,7 @@ fn send_never_deadline() {
 }
 
 #[test]
+#[ignore = "Inherently flaky and has caused several CI failures"]
 fn send_before_recv_timeout() {
     let (sender, receiver) = oneshot::channel();
 
@@ -97,7 +98,10 @@ fn send_before_recv_timeout() {
         _ => panic!("expected Ok(22)"),
     }
 
-    assert!(start.elapsed() < timeout);
+    // FIXME(#152648): Under load, there's no guarantee that the main thread is
+    // scheduled and run before this timeout expires.
+    let elapsed = start.elapsed();
+    assert!(elapsed < timeout, "expected {elapsed:?} < {timeout:?}");
 }
 
 #[test]