Readd issue-76375 with a tweak

JohnTitor · JohnTitor · commit 956e92e82a9d · 2020-09-30T10:47:22.000+09:00
diff --git a/ices/76375.sh b/ices/76375.sh
@@ -29,5 +29,5 @@ pub async fn h() {}
 
 EOF
 
-rustc --edition=2018 -Zmir-opt-level=2 x.rs
+rustc --edition=2018 -Zmir-opt-level=2 -Zunsound-mir-opts x.rs
 rustc --edition=2018 -Zmir-opt-level=2 y.rs --extern x -L.
