Allow switching to another driver build without a full installation.
Glamor already takes LIBGL_DRIVERS_PATH into account, so this change
makes sure that the same driver is used in both parts of the server.
Signed-off-by: Nicolai Hähnle <nicolai.haehnle@amd.com>
Reviewed-by: Ben Crocker <bcrocker@redhat.com>
Reviewed-by: Antoine Martin <antoine@nagafix.co.uk>
Tested-by: Ben Crocker <bcrocker@redhat.com>