egl: only check dri3 on X11
When mesa is built without support for X11 Zink will always refuse to
start unless LIBGL_KOPPER_DRI2 is set.
Only perform this check on X11 where it is relevant.
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When mesa is built without support for X11 Zink will always refuse to
start unless LIBGL_KOPPER_DRI2 is set.
Only perform this check on X11 where it is relevant.