Cannot compile OpenMesh with unittests enabled

I can not compile OpenMesh with the unittests enabled on our lab machines. I am getting compile errors from :

gtest-message.h:191
internal::StringStreamToString(ss_.get());
undefined reference to StringStreamToString(ss_.get());

The default gtest library is selected by cmake as

/ACG/acgdev/gcc-4.7-x86_64/gtest/

but since the lab machines have been updated the gcc --version command states the compiler version is 6.3.0. I tried using the gtest library from /ACG/acgdev/gcc-4.9-x86_64/gtest/ but it gives the same error.

Is this caused by incompatibilities of the older gcc versions / libraries built with it?