FTBFS: Can't use rootcling on ifarm because of old libstdc++

[DraTeots]

Any users code that needs to generate dictionaries is affected

The problem (for me at the moment it is extremely difficult to isolate the problem in one-two c++ files. But the next steps are straight forward):

source /cvmfs/eic.opensciencegrid.org/packages/setup-env.sh
spack load --first eic os=centos7
spack load --first gcc os=centos7

mkdir dirc && cd dirc
git clone https://github.com/rdom/eicdirc
git clone https://github.com/rdom/prttools
mkdir build && cd build
cmake -DCMAKE_CXX_STANDARD=17 ../eicdirc/

It fails with:

.../rootcling -v2 -f G__Prt.cxx -s /home/romanov/dirc/build/libPrt.so -rml libPrt.so -rmf /home/romanov/dirc/build/libPrt.rootmap -DG4UI_USE_TCSH -DG4INTY_USE_QT -DG4UI_USE_QT -DG4VIS_USE_OPENGLQT -DG4VIS_USE_OPENGL -I/cvmfs/eic.opensciencegrid.org/packages/clhep/2.4.1.3/linux-centos7-x86_64-gcc-9.3.0-vpphhq4z55o6paocmxi2tgsowvog3q73/lib/CLHEP-2.4.1.3/../../include -I/cvmfs/eic.opensciencegrid.org/packages/geant4/10.6.2/linux-centos7-x86_64-gcc-9.3.0-bdlgoee3hwsaszkcxbgapbmx2xjemwmc/include/Geant4 -I/cvmfs/eic.opensciencegrid.org/packages/root/6.20.04/linux-centos7-x86_64-gcc-9.3.0-qiipdiw4t4m3mgmy6mjiixfmv2poh43w/include -I/home/romanov/dirc/eicdirc/src -I/home/romanov/dirc/eicdirc -std=c++17 PrtHit.h PrtEvent.h PrtLutNode.h PrtAmbiguityInfo.h PrtPhotonInfo.h PrtTrackInfo.h /home/romanov/dirc/eicdirc/src/PrtLinkDef.h

In file included from input_line_11:18:
In file included from /home/romanov/dirc/eicdirc/src/PrtHit.h:13:

In file included from /cvmfs/eic.opensciencegrid.org/packages/root/6.20.04/linux-centos7-x86_64-gcc-9.3.0-qiipdiw4t4m3mgmy6mjiixfmv2poh43w/include/TVector3.h:16:

...

In file included from /cvmfs/eic.opensciencegrid.org/packages/root/6.20.04/linux-centos7-x86_64-gcc-9.3.0-qiipdiw4t4m3mgmy6mjiixfmv2poh43w/include/TString.h:28:

/cvmfs/eic.opensciencegrid.org/packages/root/6.20.04/linux-centos7-x86_64-gcc-9.3.0-qiipdiw4t4m3mgmy6mjiixfmv2poh43w/include/ROOT/RStringView.hxx:19:10: fatal error: 'string_view' file not found

[DraTeots]

It is a copy of #80 which was created due to GitHub network/server error.