connector c++ is not buildable with rhel7, sles12

Connector c++ requires GCC 4.9, but sles12 and rhel7 have 4.8.
Is 4.9 really needed?

the error message is confusing - "GCC versin >4.8 is required" - build error in rhel7 happens, but does not clarify the situation (rhel7 has gcc 4.8.5)

changing https://github.com/mariadb-corporation/mariadb-connector-cpp/blob/master/CMakeLists.txt#L29 4.9 -> 4.8 fixes the problem

also the condition:

IF(CMAKE_COMPILER_IS_GNUCC AND CMAKE_CXX_COMPILER_VERSION VERSION_LESS 4.9)

does not work if compiler is not gnucc and does not check its version.