Externals Update, 21.2 branch (2019.10.22.)
Updated all projects to atlasexternals-1.0.57.
The "only" change compared to the previous tag (atlasexternals@1.0.56...1.0.57) is that External/Python, External/FastJet and External/Lhapdf were updated to build successfully on macOS Catalina. So hopefully the update should not change anything at all in the CentOS 7 builds.