bug#69546: cksum: inconsistent handling of invalid length values

[Daniel Hofstetter]

Hi,

When specifying an invalid length value followed by a valid length
value I get the following error:

$ printf "hello" | cksum --algo=blake2b --length=12 --length=8
cksum: invalid length: ‘12’
cksum: length is not a multiple of 8

However, if the invalid length value is a multiple of 8 and greater
than 512 (the maximum digest length for blake2b), there is no error:

$ printf "hello" | cksum --algo=blake2b --length=123456 --length=8
BLAKE2b-8 (-) = 29

I think the behavior should be the same in the two scenarios, whether
it's showing an error or ignoring the invalid value.

I'm using coreutils 9.4.

Regards,
Daniel