v2 sha256sum: unrecognized option: check

[jdebbink]

Trying to upgrade to v2 from v1 and getting this error:

sha256sum: unrecognized option: check

Usage: sha256sum [-c[sw]] [FILE]...

Print or check SHA256 checksums

	-c	Check sums against list in FILEs
	-s	Don't output anything, status code shows success
	-w	Warn about improperly formatted checksum lines

Using the docker image.

[jdebbink]

Opened #198 to address

[afinetooth]

Closed by #227

@jdebbink thank you. Left you a comment on your PR here.