Better diagnostics when wget is missing
When wget is missing building the fedabipkgdiff tool is disabled.
This patch fixes diagnostics in that case.
* configure.ac: When wget is missing then make the disabling of
the building of the fedabipkgdiff tool show up in the
configuration summary and emit a notice.
Signed-off-by: Dodji Seketeli <dodji@redhat.com>