cmake LWS_HAVE_VFORK_H examples

warmcat/libwebsockets CMakeLists.txt :682 

CHECK_C_SOURCE_COMPILES("#include <vfork.h>\nvoid main(void) { while(1) ; } void xxexit(void){}" LWS_HAVE_VFORK_H)

c-jimenez/open-ocpp 3rdparty/libwebsockets/CMakeLists.txt :646 

CHECK_INCLUDE_FILE(vfork.h LWS_HAVE_VFORK_H)

fluffos/fluffos src/thirdparty/libwebsockets/CMakeLists.txt :629 

CHECK_INCLUDE_FILE(vfork.h LWS_HAVE_VFORK_H)