Adding CAP_NET_RAW to binaries

Hi,

I'm building the prometheus blackbox exporter that needs the CAP_NET_RAW capability to
conduct ICMP probes (I don't want to run it as root)

I've done the naïve 
setcap cap_net_raw+ep
/builddir/build/BUILDROOT/prometheus-blackbox-exporter-0.10.0-1.fc28.llt.x86_64/usr/bin/prometheus-blackbox-exporter

in the specfile, but that makes mock barf
unable to set CAP_SETFCAP effective capability: Operation not permitted

What is the correct way to handle this?

Regards,

-- 
Nicolas Mailhot