Apparently mesa 22.3.0 has updated the egl headers, and eglplatform.h now
contains commit
3670d645f4
after which xlib headers don't get included by default anymore but are
dependent upon whether USE_X11 was defined.
This breaks headless builds of gstreamer-vaapi because we always define
an internal define USE_X11 as either 1 or 0.
Change these defines to GST_VAAPI_USE_XYZ instead to avoid this.
Fixes#1634
Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/3555>