cmake HAVE_INC_MSG_H examples

CTSRD-CHERI/cheribsd contrib/libpcap/CMakeLists.txt :2600 

check_include_file(msg.h HAVE_INC_MSG_H)

asset-group/5ghoul-5g-nr-attacks libs/libpcap/CMakeLists.txt :1780 

check_include_file(msg.h HAVE_INC_MSG_H)