Merge pull request #1203 from reyoung/feature/fix_runtime_error_in_macos

Make external/glog use local gflags.

cmake/external/glog.cmake

@@ -36,6 +36,7 @@ ExternalProject_Add(
     CMAKE_ARGS      -DCMAKE_INSTALL_PREFIX=${GLOG_INSTALL_DIR}
     CMAKE_ARGS      -DCMAKE_POSITION_INDEPENDENT_CODE=ON
     CMAKE_ARGS      -DWITH_GFLAGS=ON
+    CMAKE_ARGS      -Dgflags_DIR=${GFLAGS_INSTALL_DIR}/lib/cmake/gflags
     CMAKE_ARGS      -DBUILD_TESTING=OFF
 )