fix ld bug when enable WITH_TESTING

cmake/external/gtest.cmake

@@ -34,9 +34,15 @@ IF(WITH_TESTING)
             "${GTEST_INSTALL_DIR}/lib/libgtest_main.a" CACHE FILEPATH "gtest main libraries." FORCE)
     ENDIF(WIN32)
 
+    IF(WITH_MKL_LITE)
+        # wait for mkl downloading completed
+        SET(GTEST_DEPENDS   ${MKL_LITE_PROJECT})
+    ENDIF()
+
     ExternalProject_Add(
         extern_gtest
         ${EXTERNAL_PROJECT_LOG_ARGS}
+        DEPENDS         ${GTEST_DEPENDS}
         GIT_REPOSITORY  "https://github.com/google/googletest.git"
         GIT_TAG         "release-1.8.0"
         PREFIX          ${GTEST_SOURCES_DIR}