Ignore p2_udp_send_to_closed_receiver on macOS (#14031)

This [failed on CI recently][log] and it was already flaky on Windows.
Maybe eventually we'll just remove this test for flakiness, but for now
I'd like to keep flaky tests out of the critical path of the merge
queue.

[log]: https://github.com/bytecodealliance/wasmtime/actions/runs/30563046634/job/90940763865

Author: alexcrichton

crates/wasi/tests/all/p2/async_.rs

@@ -372,6 +372,9 @@ async fn p2_udp_connect() {
     run(P2_UDP_CONNECT_COMPONENT, |_| {}).await.unwrap()
 }
 #[test_log::test(tokio::test(flavor = "multi_thread"))]
+// See the comment on the `p2::sync` variation of this test; for why this is
+// ignored on macos
+#[cfg_attr(target_os = "macos", ignore)]
 async fn p2_udp_send_to_closed_receiver() {
     run(P2_UDP_SEND_TO_CLOSED_RECEIVER_COMPONENT, |_| {})
         .await

crates/wasi/tests/all/p2/sync.rs

@@ -350,6 +350,11 @@ fn p2_udp_connect() {
 // consistently fails when run in combination with the `p2::async_` variation,
 // and we've thus far been unable to determine the reason.
 #[cfg_attr(windows, ignore = "This test is flaky on Windows.")]
+// This test is flaky on macOS in CI. One possible reason is that this relies on
+// a port being closed which concurrent tests can otherwise re-bind. Another
+// reason is that maybe this is just flaky on macOS (LLMs say something about
+// the OS rate-limiting ICMP messages if they're to be believed).
+#[cfg_attr(target_os = "macos", ignore = "This test is flaky on macOS.")]
 fn p2_udp_send_to_closed_receiver() {
     run(P2_UDP_SEND_TO_CLOSED_RECEIVER_COMPONENT, |_| {}).unwrap()
 }