glx: meson: wire up the dispatch-index-check test

Accidentally dropped with earlier commit.!

Fixes: 4ccb9816 ("meson: Use consistent style for tests")
Signed-off-by: Emil Velikov <emil.velikov@collabora.com>
Reviewed-by: Dylan Baker <dylan@pnwbakers.com>
(cherry picked from commit e139d7a8)