Use `os_unfair_lock` on Apple platforms

core/os/spin_lock.h

@@ -33,6 +33,25 @@
 
 #include "core/typedefs.h"
 
+#if defined(__APPLE__)
+
+#include <os/lock.h>
+
+class SpinLock {
+	mutable os_unfair_lock _lock = OS_UNFAIR_LOCK_INIT;
+
+public:
+	_ALWAYS_INLINE_ void lock() const {
+		os_unfair_lock_lock(&_lock);
+	}
+
+	_ALWAYS_INLINE_ void unlock() const {
+		os_unfair_lock_unlock(&_lock);
+	}
+};
+
+#else
+
 #include <atomic>
 
 class SpinLock {
@@ -49,4 +68,6 @@ public:
 	}
 };
 
+#endif // __APPLE__
+
 #endif // SPIN_LOCK_H