It is built by porting InfiniDB 4.6.7 on MariaDB and adding entirely new features not found anywhere else.
This repository is not meant to be built independently outside of MariaDB server.
https://github.com/MariaDB/server/tree/10.8
See building instructions here.
Issue tracking of MariaDB ColumnStore happens in JIRA, https://jira.mariadb.org/browse/MCOL