Why is gnutls-3.4.7 needed for samba-4.8.0 with "--with-dc" enabled?

[Nico Kadel-Garcia]

I've been looking at backporting Samba 4.8.0 to RHEL and CentOS 7, and
see that there is a hard-coded dependency for gnutls 3.4.7 or later
iif "--with-dc" is enabled. Backporting gnutls-3.4.7 into RHEL or
CentOS 7 is.... a lot more work than I'd personally want to take on.

Is the dependency on gnutls-3.4.7 a hard dependency?