This should basically just mean doing a standard maven build of openmrs-core, with an environment variable set to point to an external database (instead of the in-memory H2 one)
Per Lluis’s comment at Support for MariaDB: Looking for volunteers we may need to reapply a commit to be able to run context-sensitive tests during the regular OpenMRS build against an external DB based on an environment variable
probably the easiest way to get a clean mariadb/mysql is to use the docker tricks that Cintia and Mario worked out. You may also need to use the openmrs sdk to create the structure of the database