This is an early patch to use as a discussion support, only tested on CentOS 8 on master with GDAL 3.2, to add the generation of gdal*-java RPMs.

This is a follow-up to the accepted PR sent to fedora to re-enable gdal-java RPMs generation for EPEL 8 (https://src.fedoraproject.org/rpms/gdal/pull-request/18).
GDAL-Java RPMs support is a technical need for my GeoServer, and I'm already using postgres' GDAL RPMs there, so being able to install a single GDAL version in the environment would be a plus.