glmark2: Remove X11 exclusiveness

The tool has support for multiple backends: X11, drm and Wayland.

This demanded to a fix, which has been sent upstream, to make the
flavor configuration predictable and the recipe has been rework to
support them all, making the PACKAGECONFIG to respect the
DISTRO_FEATURES available by default.

Signed-off-by: Otavio Salvador <otavio@ossystems.com.br>
Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>