build: add tar.xz target

kup generates .xz files, and fedora RPMs now use that.
It'd be nice to have a handy target to generate .xz
files locally, so hack that in.

Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Reviewed-by: Bill O'Donnell <billodo@redhat.com>
Signed-off-by: Eric Sandeen <sandeen@sandeen.net>
1 file changed