[Graph]: fix a linking error when optimization flag is disabled.
[Graph]: fix a linking error when optimization flag is disabled.

flashxio/FlashX,flashxio/FlashX,zheng-da/FlashX,flashxio/FlashX,icoming/FlashGraph,icoming/FlashGraph,icoming/FlashGraph,zheng-da/FlashX,flashxio/FlashX,flashxio/FlashX,icoming/FlashX,zheng-da/FlashX,flashxio/FlashX,zheng-da/FlashX,icoming/FlashX,zheng-da/FlashX,icoming/FlashX,icoming/FlashGraph,icoming/FlashX,icoming/FlashGraph,icoming/FlashX