Use DebugSyncStream where appropriate.

Author: alliepiper

thrust/system/cuda/detail/core/agent_launcher.h

@@ -514,9 +514,7 @@ namespace core {
     {
       if (debug_sync)
       {
-        NV_IF_TARGET(NV_IS_HOST,
-                     (cudaStreamSynchronize(stream);),
-                     (cub::detail::device_synchronize();));
+        cub::DebugSyncStream(stream);
       }
     }