cmake HAVE_CAP_GETHOSTBYADDR examples

CTSRD-CHERI/cheribsd contrib/tcpdump/CMakeLists.txt :1038 

check_library_exists(cap_dns cap_gethostbyaddr "" HAVE_CAP_GETHOSTBYADDR)

CTSRD-CHERI/cheribsd contrib/tcpdump/CMakeLists.txt :1043 

endif(HAVE_CAP_GETHOSTBYADDR)