x11/py-sip doesn't build with python311

[adr <adr%SDF.ORG@localhost>]

Hi,

I'm using this patch from fedora, maybe someone with experience
with siplib can evaluate it. Don't ask me.

https://bugzilla.redhat.com/show_bug.cgi?id=2062144

x11/py-sip/patch-siplib_siplib.c:

$NetBSD$
--- siplib/siplib.c.orig	2021-02-26 15:17:35.147922000 +0000
+++ siplib/siplib.c
@@ -13747,7 +13747,7 @@ static struct _frame *sip_api_get_frame(

     while (frame != NULL && depth > 0)
     {
-        frame = frame->f_back;
+        frame = PyFrame_GetBack(frame);
         --depth;
     }