Build a cmsgemos version ROOT with C++17

Description

The ROOT framework has this "feature" that requires the software to be built with the exact same C++ version as the library. We build cmsgemos with C++17 while the ROOT library provided in the EPEL repositories is built with C++11. This makes the compilation impossible, not even mentioning the running.

Possible fixes

Buil a custom GEM ROOT version similar to what is done for DPDK. The output RPMs should conflict with the EPEL version in order to avoid further conflicts. It must be noted that HCAL follows a similar approach.