b2sum -l X is missing

[sylvestre]

$ /usr/bin/b2sum -l 0 /dev/null
786a02f742015903c6c6fd852552d272912f4740e15847618a86e217f71f5419d25e1031afee585313896444934eb04b903a685b1448b755d56f701afe9be2ce  /dev/null

or
b2sum -l 128 /dev/null

On our side:

$ b2sum -l 0 /dev/null
error: Found argument '-l' which wasn't expected, or isn't valid in this context

  If you tried to supply '-l' as a value rather than a flag, use '-- -l'

Usage: b2sum [OPTIONS] [FILE]...

Run test:
bash util/run-gnu-test.sh tests/misc/b2sum.sh