Add mingw build conditional
    
    There are many unmet mingw build requires for epel and
    current need to have epel gdal mingw packages.  So add a mingw conditional
    similar to libkml and libspatialite.
    
    Java building works on RHEL 9, so limit the RHEL check to just 8
    
    Signed-off-by: Tom Rix <trix@redhat.com>