freebsd: disable forking in preconnect sandbox

src/xmppipe_sandbox_capsicum.c

@@ -26,6 +26,11 @@
     int
 xmppipe_sandbox_init(xmppipe_state_t *state)
 {
+    struct rlimit rl = {0};
+
+    if (setrlimit(RLIMIT_NPROC, &rl) < 0)
+        return -1;
+
     return 0;
 }