cmake LIBXNET_HAS_RECVMSG examples

CTSRD-CHERI/cheribsd contrib/libpcap/CMakeLists.txt :886 

check_library_exists(xnet recvmsg "" LIBXNET_HAS_RECVMSG)

CTSRD-CHERI/cheribsd contrib/libpcap/CMakeLists.txt :896 

endif(LIBXNET_HAS_RECVMSG)

asset-group/5ghoul-5g-nr-attacks libs/libpcap/CMakeLists.txt :550 

check_library_exists(xnet recvmsg "" LIBXNET_HAS_RECVMSG)

asset-group/5ghoul-5g-nr-attacks libs/libpcap/CMakeLists.txt :557 

endif(LIBXNET_HAS_RECVMSG)