Nettle 2.6 (released in 2013) split the sha.h header into sha1.h & sha2.h,
but left the sha.h header for compatibility until the recent Nettle 4.0
release finally removed it.
Nettle 4.0 also dropped the length argument from the sha1_digest function.
Closes: #1871
Signed-off-by: Alan Coopersmith <alan.coopersmith@oracle.com>
Part-of: <https://gitlab.freedesktop.org/xorg/xserver/-/merge_requests/2133>