cmake LIBNETWORK_HAS_GETHOSTBYADDR examples

CTSRD-CHERI/cheribsd contrib/tcpdump/CMakeLists.txt :464 

check_library_exists(network gethostbyaddr "" LIBNETWORK_HAS_GETHOSTBYADDR)

CTSRD-CHERI/cheribsd contrib/tcpdump/CMakeLists.txt :467 

else(LIBNETWORK_HAS_GETHOSTBYADDR)

CTSRD-CHERI/cheribsd contrib/tcpdump/CMakeLists.txt :469 

endif(LIBNETWORK_HAS_GETHOSTBYADDR)