cmake: make sure libz is at end of link if enabled
cmake: make sure libz is at end of link if enabled

https://github.com/warmcat/libwebsockets/issues/1840
sartura/libwebsockets,sartura/libwebsockets,sartura/libwebsockets,sartura/libwebsockets,sartura/libwebsockets,sartura/libwebsockets,sartura/libwebsockets