classpath: Use an include file for x11 feature check

This will make it easier to maintain reflecting the same distro check on
packages depending on classpath (in the dependency chain)

The patch is waiting upstream inclusion in the kirkstone branch:
https://lists.openembedded.org/g/openembedded-devel/message/98292



Signed-off-by: Andrei Gherzan <andrei.gherzan@huawei.com>