Make append and setLastQueuedCommand atomic

Two threads can enqueue to the same HostQueue (HostQueue::enqueue)
and result in last queued command being the first one reachine queue_.enqueue

NOTE: Temporarly make setLastQueuedCommand empty function to pass the build

Change-Id: Id09c3a28d184986f52b2ec86a2f6a18c40df1f0b

rocclr/platform/commandqueue.hpp

@@ -236,7 +236,7 @@ class HostQueue : public CommandQueue {
   Command* getLastQueuedCommand(bool retain);
 
   //! Set last enqueued command
-  void setLastQueuedCommand(Command* lastCommand);
+  void setLastQueuedCommand(Command* lastCommand) {}
 };