[libvirt] Can we make sc_copyright_check non-fatal?

[Cole Robinson]

The copyright date syntax check is a source of frustration for me:

- It fails on old maint branches.

- It pokes into non git managed directories in $(srcdir). I like to keep
directories like f18-maint.git, f19-maint.git etc. that are checkouts of the
respective maint branches so I can parallelize when doing maint builds, and I
like to keep them in my libvirt.git dir for organization, but running
syntax-check in libvirt.git fails on the copyright check in
$(srcdir)/f18-maint.git/.gnulib/...

Is there any way to make it non-fatal? If it still spams with all the
'failures' I'm sure that's enough to encourage fixing the issues without
blocking valid usage.

Thanks,
Cole