Move to LCG_98python3_ATLAS_3
Not tested locally, so taking advantage of quieter CI over the weekend to do it.
https://sft.its.cern.ch/jira/browse/SPI-1755
Here is the cmake: https://gitlab.cern.ch/sft/lcgcmake/-/blob/LCG_98/cmake/toolchain/heptools-98python3_ATLAS_3.cmake
Ping @fwinkl @elmsheus @rhauser
@amete this has the new gperftool version
Edited by Edward Moyse