Move directives outside rb_ary_new3 call

This function may be a macro for optimization, which will be expanded
to `rb_ary_new_from_values`.

```
ext/socket/ancdata.c: In function ‘bsock_recvmsg_internal’:
ext/socket/ancdata.c:1648:1: error: embedding a directive within macro arguments is not portable
 1648 | #if defined(HAVE_STRUCT_MSGHDR_MSG_CONTROL)
      | ^
ext/socket/ancdata.c:1650:1: error: embedding a directive within macro arguments is not portable
 1650 | #else
      | ^
ext/socket/ancdata.c:1652:1: error: embedding a directive within macro arguments is not portable
 1652 | #endif
      | ^
```

ext/socket/ancdata.c

@@ -1643,14 +1643,14 @@ bsock_recvmsg_internal(VALUE sock,
         rb_obj_reveal(dat_str, rb_cString);
     }
 
-    ret = rb_ary_new3(3, dat_str,
-                         rsock_io_socket_addrinfo(sock, mh.msg_name, mh.msg_namelen),
 #if defined(HAVE_STRUCT_MSGHDR_MSG_CONTROL)
-                         INT2NUM(mh.msg_flags)
+    VALUE msg_flags = INT2NUM(mh.msg_flags);
 #else
-                         Qnil
+    VALUE msg_flags = Qnil;
 #endif
-                         );
+    ret = rb_ary_new3(3, dat_str,
+                         rsock_io_socket_addrinfo(sock, mh.msg_name, mh.msg_namelen),
+                         msg_flags);
 
 #if defined(HAVE_STRUCT_MSGHDR_MSG_CONTROL)
     family = rsock_getfamily(fptr);