autotools: error out when using the broken --with-{gl, osmesa}-lib-name

The toggles were broken with the introduction of --enable-mangling.
Fixing that up might be possible, but it's not worth the complexity
since one can rename the libraries at any point.

CC: <mesa-stable@lists.freedesktop.org>
Signed-off-by: Emil Velikov <emil.velikov@collabora.com>
Reviewed-by: Adam Jackson <ajax@redhat.com>
(cherry picked from commit d5ac2364)