Comment # 3 on bug 1095670 from Dr. Werner Fink

(In reply to Jan Ritzerfeld from comment #2)
> POS36-C: "Consequently, it is recommended that a program relinquish
> supplementary group IDs immediately before relinquishing root privileges."
> rpmlint warns about a missing-call-to-setgroups-before-setuid.

That is the reason why the setgroup is there:

@@ -1277,6 +1278,7 @@ disable_priv_mode ()
 {
   int e;

+  setgroups(0, NULL);
   if (setuid (current_user.uid) < 0)
     {
       e = errno;


...maybe the initgroups(3) (g)libc call would be better as this does inherent
setgroups(2) with users groups as well.  Also it would help if rpmlint would
mention initgroups(3) as the better option