cmake LWS_HAVE_FORK examples

warmcat/libwebsockets CMakeLists.txt :643 

CHECK_FUNCTION_EXISTS(fork LWS_HAVE_FORK)

c-jimenez/open-ocpp 3rdparty/libwebsockets/CMakeLists.txt :567 

CHECK_FUNCTION_EXISTS(fork LWS_HAVE_FORK)

fluffos/fluffos src/thirdparty/libwebsockets/CMakeLists.txt :550 

CHECK_FUNCTION_EXISTS(fork LWS_HAVE_FORK)