Either modify dnssd/CMakeLists.txt to emit MESSAGE()-s logging the branch
conditions or traversed branches, or use ldd to check wether or not
mDNSResponders' libdns_sd.so is referenced by ${PREFIX}/lib/libkdnssd.so of the
built port, which it should be iff kdelibs4's ZEROCONF port option is
MDNSRESPONDER.