cmake HAVE_CAP_INIT examples

CTSRD-CHERI/cheribsd contrib/tcpdump/CMakeLists.txt :1034 

check_library_exists(casper cap_init "" HAVE_CAP_INIT)

CTSRD-CHERI/cheribsd contrib/tcpdump/CMakeLists.txt :1044 

endif(HAVE_CAP_INIT)