cmake HAVE_STRUCT_ETHER_ADDR examples

CTSRD-CHERI/cheribsd contrib/tcpdump/CMakeLists.txt :712

check_struct_has_member("struct ether_addr" octet "sys/types.h;sys/socket.h;net/if.h;netinet/in.h;netinet/if_ether.h" HAVE_STRUCT_ETHER_ADDR)