meson: add support for xlib glx

There is a bunch of churn in the main meson.build so that we can
correctly set the auto tristate of GLX. In particular, don't build
xlib-based glx when dri and gallium are disabled but vulkan is enabled,
in that case just turn glx off.

Signed-off-by: Dylan Baker <dylanx.c.baker@intel.com>
Reviewed-by: Eric Anholt <eric@anholt.net>
3 files changed