make Apple futex test not depend on scheduler behaviour

Author: joboet

tests/pass-dep/concurrency/apple-futex.rs

@@ -1,4 +1,5 @@
 //@only-target: darwin
+//@compile-flags: -Zmiri-preemption-rate=0
 
 use std::time::{Duration, Instant};
 use std::{io, ptr, thread};
@@ -173,7 +174,7 @@ fn wait_wake_multiple() {
                 );
             });
 
-            thread::sleep(Duration::from_millis(200));
+            thread::yield_now();
         }
 
         // Wake the threads up again.
@@ -230,7 +231,7 @@ fn param_mismatch() {
         });
 
         s.spawn(|| {
-            thread::sleep(Duration::from_millis(200));
+            thread::yield_now();
             unsafe {
                 assert_eq!(
                     libc::os_sync_wait_on_address(
@@ -246,7 +247,8 @@ fn param_mismatch() {
             }
         });
 
-        thread::sleep(Duration::from_millis(200));
+        thread::yield_now();
+
         unsafe {
             assert_eq!(
                 libc::os_sync_wake_by_address_any(