Core::SetState: Avoid Global System Accessor

Source/Core/Core/Core.h

@@ -143,7 +143,7 @@ bool IsHostThread();
 bool WantsDeterminism();
 
 // [NOT THREADSAFE] For use by Host only
-void SetState(State state, bool report_state_change = true);
+void SetState(Core::System& system, State state, bool report_state_change = true);
 State GetState(Core::System& system);
 
 void SaveScreenShot();