[sftp] generate debug header at build time (this requires kf5.14)
Summary:
now use having boilerplate code sit around, pretty much the same stuff is
generated by ECM. KF 5.14 is ancient, so it should be good to require.
Reviewers: broulik
Reviewed By: broulik
Differential Revision: https://phabricator.kde.org/D15453