Make sure atomic_init is declared.
@@ -73,6 +73,7 @@ __FBSDID("$FreeBSD: head/sys/netinet/sctp_pcb.c 349998 2019-07-15 14:52:52Z tuex
#endif
#if defined(__Userspace__)
#include <user_socketvar.h>
+#include <user_atomic.h>
#if !defined(__Userspace_os_Windows)
#include <netdb.h>
#endif
