Tag to be used with the main branch of atlas/athena. Update(s) since 2.1.0: - Patched VecGeom to handle arguments in $CXX correctly; - Patched yampl to handle arguments in $CXX correctly; - Updated all projects to use LCG_104b_ATLAS_1 by default; - Explicitly disabled the use of ZSTD in the build of Gdb; - Patched GeoModel to use $CXXFLAGS correctly.