Two small things:

> -MODCARGO_CRATES +=	ring	0.17.5	# LICENSE
> +MODCARGO_CRATES +=	ring	0.17.7	# LICENSE

crates.inc no longer contains ring 0.16, so the BDEP on rust-ring can
be dropped and the NOT_FOR_ARCHS should be changed to:

# ring-v0.17 does not support this arch
NOT_FOR_ARCHS =         sparc64