cmake LIBSOCKET_HAS_GETHOSTBYADDR examples

CTSRD-CHERI/cheribsd contrib/tcpdump/CMakeLists.txt :456 

check_library_exists(socket gethostbyaddr "" LIBSOCKET_HAS_GETHOSTBYADDR)

CTSRD-CHERI/cheribsd contrib/tcpdump/CMakeLists.txt :459 

else(LIBSOCKET_HAS_GETHOSTBYADDR)

CTSRD-CHERI/cheribsd contrib/tcpdump/CMakeLists.txt :471 

endif(LIBSOCKET_HAS_GETHOSTBYADDR)