devel/boost-libs: unbreak some C++14 consumers with GCC after r479222
Boost 1.68 changed System ABI for C++14 but due to a GCC bug it's
disabled for C++ >= 17. As our Boost package is built in C++17
consumers cannot use C++14. So, disable the new ABI for the affected
GCC versions regardless of C++ standard.
Reported by: Piotr Kubaj