security/zeek: Unbreak PERFTOOLS
Apparently the pprof has been provided by the devel/pprof port for
quite awhile. Since PERFTOOLS is off by default this wasn't noticed
until reported by Andrea Venturoli.
Reported by: Andrea Venturoli
(cherry picked from commit e0559cfd0cdebe8fb98a1f46b5a183539e9ee569)