Add Platform::Yield

Source/Engine/Platform/Apple/ApplePlatform.cpp

@@ -293,6 +293,11 @@ void ApplePlatform::Sleep(int32 milliseconds)
     usleep(milliseconds * 1000);
 }
 
+void ApplePlatform::Yield()
+{
+    pthread_yield();
+}
+
 double ApplePlatform::GetTimeSeconds()
 {
     return SecondsPerCycle * mach_absolute_time();

Source/Engine/Platform/Apple/ApplePlatform.h

@@ -75,6 +75,7 @@ public:
     static void SetThreadPriority(ThreadPriority priority);
     static void SetThreadAffinityMask(uint64 affinityMask);
     static void Sleep(int32 milliseconds);
+    static void Yield();
     static double GetTimeSeconds();
     static uint64 GetTimeCycles();
     static uint64 GetClockFrequency();