make java runtime dependency optional

make java runtime dependency optional

it appears lo uses java only for selected components and runs fine
without it. additionally java(ClassDataVersion) dependency mandates
installation of default jre that provides given java(ClassDataVersion)
meaning jre 8 cannot be installed cleanly as the default jre since lo
requires jre >= 9. lo however does not rely on default jre and scans
%{_libdir}/jvm for all available installations and is perfectly fine
with just *-jre-base package.

therefore disable java(ClassDataVersion) dependency and suggest jre used
during build instead.