Rollup merge of #92121 - RalfJung:miri-core-test, r=kennytm

disable test with self-referential generator on Miri

Running the libcore test suite in Miri currently fails due to the known incompatibility of self-referential generators with Miri's aliasing checks (rust-lang/unsafe-code-guidelines#148). So let's disable that test in Miri for now.

library/core/tests/future.rs

@@ -30,6 +30,7 @@ fn poll_n(val: usize, num: usize) -> PollN {
 }
 
 #[test]
+#[cfg_attr(miri, ignore)] // self-referential generators do not work with Miri's aliasing checks
 fn test_join() {
     block_on(async move {
         let x = join!(async { 0 }).await;