dont use the vendored gtest
Index: cmake/test.cmake
--- cmake/test.cmake.orig
+++ cmake/test.cmake
@@ -12,6 +12,4 @@ if (WITH_TESTS)
     add_definitions(/D _VARIADIC_MAX=10)
   endif()
 
-  include_directories(${ROOT_DIR}/vendor/gtest/include
-      ${ROOT_DIR}/vendor/gtest)
 endif()
