std: do not use dispatch semaphore under miri (yet)

Author: joboet

Diff for: library/std/src/sys/unix/thread_parker/mod.rs

@@ -11,11 +11,14 @@
 )))]
 
 cfg_if::cfg_if! {
-    if #[cfg(any(
-        target_os = "macos",
-        target_os = "ios",
-        target_os = "watchos",
-        target_os = "tvos",
+    if #[cfg(all(
+        any(
+            target_os = "macos",
+            target_os = "ios",
+            target_os = "watchos",
+            target_os = "tvos",
+        ),
+        not(miri),
     ))] {
         mod darwin;
         pub use darwin::Parker;