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>