spec: Add support for building the zfs storage driver
spec: Add support for building the zfs storage driver

Where it can be supported in Fedora, the driver is built and made
available as a subpackage.

Signed-off-by: Neal Gompa <8135daa3762340227c0c67f1c47ad07a127bd3a3@gmail.com>

datto/libvirt,crobinso/libvirt,crobinso/libvirt,datto/libvirt,olafhering/libvirt,crobinso/libvirt,andreabolognani/libvirt,olafhering/libvirt,andreabolognani/libvirt,libvirt/libvirt,libvirt/libvirt,jardasgit/libvirt,eskultety/libvirt,eskultety/libvirt,jfehlig/libvirt,nertpinx/libvirt,jfehlig/libvirt,datto/libvirt,nertpinx/libvirt,jfehlig/libvirt,datto/libvirt,fabianfreyer/libvirt,nertpinx/libvirt,jfehlig/libvirt,olafhering/libvirt,jardasgit/libvirt,andreabolognani/libvirt,fabianfreyer/libvirt,eskultety/libvirt,nertpinx/libvirt,jardasgit/libvirt,jardasgit/libvirt,zippy2/libvirt,olafhering/libvirt,andreabolognani/libvirt,nertpinx/libvirt,eskultety/libvirt,zippy2/libvirt,andreabolognani/libvirt,zippy2/libvirt,crobinso/libvirt,fabianfreyer/libvirt,libvirt/libvirt,fabianfreyer/libvirt,jardasgit/libvirt,fabianfreyer/libvirt,zippy2/libvirt,eskultety/libvirt,libvirt/libvirt,datto/libvirt