ci/deqp: ensure that in `default` builds, wayland + x11 + xcb are all built
If someone were to remove the libraries that are needed for these,
default
would simply not enable these tests, and the only thing we
could notice is that test jobs would suddenly take less time to run.
Instead, let's have a check to make sure dEQP's cmake has detected everything and enabled these platforms.
Follow-up to !26896 (comment 2232977)