phpunit 8 / build on sid necessary?

phpunit is updated to version 8 on debian sid. the package builds on debian buster with phpunit 7.5 thanks to the patch.

since we currently target on debian buster and pma 5 already allows phpunit 8, I don't think we should update the patches for sid/phpunit8 because it's not worth the effort IMHO.

But: how should we upload? can we upload a package which does not build on sid but on buster? or do we need to create a branch buster-backports and use different version-numbers because of non-identical contents in the source-packages (with disabled tests for sid). In that case I'd prefer to disable the tests while building at all and reenable them once the package is in the backports (and then make a branch)