Licence is always required in config.ini, even if not used [rt.cpan.org #74754]

[rjbs]

https://rt.cpan.org/Ticket/Display.html?id=74754

Dist::Zilla::_build_licence blows up if there is no licence configured
in ~/.dzil/config.ini, even if it is not used or needed - for example if
the minting profile specifies its own licence in a dist.ini provided in
a template.

The error reported is: "no license data in config, no %Rights stash,
couldn't make a good guess at license from Pod; giving up".  This should
only happen after conclusively determining that licence information has
not been provided from any other source (i.e. when filling in the
licence field while generating the dist.ini).