Migration to Modern CMake

For the record, I’ve updated the old Jira issue about this subject with my latest progress :

https://alice.its.cern.ch/jira/browse/O2-419?focusedCommentId=231715&page=com.atlassian.jira.plugin.system.issuetabpanels%3Acomment-tabpanel#comment-231715

Feel free to comment there.