Update debug build scripts

I finally switched to standard "make rpm" thing

Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com>
reporter-rhtsupport: factor out tarball creation

This change doesn't change the logic, it only moves code
into a helper function.

Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com>