autotools: don't build libGLES*.so with GLVND

autotools: don't build libGLES*.so with GLVND

GLVND already provides these, so distro packagers have been deleting
them all along. Let's save ourselves the trouble and not build them in
the first place.

Signed-off-by: Eric Engestrom <eric.engestrom@intel.com>
Reviewed-by: Matt Turner <mattst88@gmail.com>
Reviewed-by: Dylan Baker <dylan@pnwbakers.com>
Reviewed-by: Emil Velikov <emil.velikov@collabora.com>