[Matrix]: fix compilation error from openmp in clang.
[Matrix]: fix compilation error from openmp in clang.

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