cmake: fix up gtest and set -fvisibility=hidden globally
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 35ecafd..b14daee 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -18,6 +18,7 @@
     set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} ${COMMON_COMPILE_FLAGS}")
     if (UNIX)
         set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -fvisibility=hidden")
+        set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -fvisibility=hidden")
     endif()
 endif()