cmake HAVE_TCP_KEEPIDLE examples

htcondor/htcondor build/cmake/CondorConfigure.cmake :341 

check_symbol_exists(TCP_KEEPIDLE "sys/types.h;sys/socket.h;netinet/tcp.h" HAVE_TCP_KEEPIDLE)

syslog-ng/syslog-ng CMakeLists.txt :144 

check_symbol_exists(TCP_KEEPIDLE  "sys/socket.h;netinet/in.h;netinet/tcp.h" HAVE_TCP_KEEPIDLE)