If you want to stay more up to date but don't want to install from source, there is the following deb file which creates a stand-alone installation of Gant with all the dependencies it needs, including Groovy 2.1.0:
Gant 1.9.9 10 standalone
The page https://admin.fedoraproject.org/pkgdb/acls/name/gant details all the Gant packages for the various Fedora versions. Sadly it seems they haven't progressed beyond 1.8.1. If there are any Fedora users out there who can contact the Fedora packagers to get them to update to the latest version that would be good.