Tag to be used with the 21.X branches of atlas/athena. Updates in this tag: - Sped up the build of LibXml2 and Python a little, by allowing the CMake build to use multiple processes for building these externals. - Added Davix 0.6.7 as a new external to AnalysisBaseExternals and AthAnalysisExternals, to be able to use the latest HTTP based file access protocols with ROOT in the analysis releases. - Updated the XRootD package to build version 4.8.2. This is to fix the issue with reading files from older versions of dCache that showed up on certain grid sites. Added the build of XRootD to AthAnalysisExternals as well. - Removed the dmtcp package from the repository. - Fixed an issue introduced in 1.0.34 with the build of the .pyc modules, which would show up for some non-standard package layouts.