xl2tpd fails to connect after upgrading to 22.04

[Kirill Kozlovskiy]

After the update from 21.10 to 22.04 beta my vpn connection via l2tp/ipsec is not working anymore.

```
Apr 03 14:30:05 my-XPS-13-9360 nm-l2tp-service[186365]: xl2tpd started with pid 186513
Apr 03 14:30:05 my-XPS-13-9360 NetworkManager[186513]: xl2tpd[186513]: Not looking for kernel SAref support.
Apr 03 14:30:05 my-XPS-13-9360 NetworkManager[186513]: xl2tpd[186513]: Using l2tp kernel support.
Apr 03 14:30:05 my-XPS-13-9360 NetworkManager[186513]: xl2tpd[186513]: xl2tpd version xl2tpd-1.3.16 started on my-XPS-13-9360 PID:186513
Apr 03 14:30:05 my-XPS-13-9360 NetworkManager[186513]: xl2tpd[186513]: Written by Mark Spencer, Copyright (C) 1998, Adtran, Inc.
Apr 03 14:30:05 my-XPS-13-9360 NetworkManager[186513]: xl2tpd[186513]: Forked by Scott Balmos and David Stipp, (C) 2001
Apr 03 14:30:05 my-XPS-13-9360 NetworkManager[186513]: xl2tpd[186513]: Inherited by Jeff McAdams, (C) 2002
Apr 03 14:30:05 my-XPS-13-9360 NetworkManager[186513]: xl2tpd[186513]: Forked again by Xelerance (www.xelerance.com) (C) 2006-2016
Apr 03 14:30:05 my-XPS-13-9360 NetworkManager[186513]: xl2tpd[186513]: Listening on IP address 0.0.0.0, port 43559
Apr 03 14:30:05 my-XPS-13-9360 NetworkManager[186513]: xl2tpd[186513]: Connecting to host MASKED_IP, port 1701
Apr 03 14:30:05 my-XPS-13-9360 NetworkManager[186513]: xl2tpd[186513]: Can not find tunnel 83 (refhim=0)
Apr 03 14:30:05 my-XPS-13-9360 NetworkManager[186513]: xl2tpd[186513]: network_thread: unable to find call or tunnel to handle packet. call = 23931, tunnel = 83 Dumping.
Apr 03 14:30:06 my-XPS-13-9360 NetworkManager[186513]: xl2tpd[186513]: Can not find tunnel 83 (refhim=0)
Apr 03 14:30:06 my-XPS-13-9360 NetworkManager[186513]: xl2tpd[186513]: network_thread: unable to find call or tunnel to handle packet. call = 23931, tunnel = 83 Dumping.
...
Apr 03 14:30:19 my-XPS-13-9360 NetworkManager[186513]: xl2tpd[186513]: death_handler: Fatal signal 15 received
Apr 03 14:30:19 my-XPS-13-9360 NetworkManager[186513]: xl2tpd[186513]: Connection 0 closed to MASKED_IP, port 1701 (Server closing)
```

Building from raw sources fix the issue: https://github.com/xelerance/xl2tpd/issues/230

Some discussion here: https://answers.launchpad.net/ubuntu/+question/701185

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[msaxl (saxl)]

@iamfuss got it working with this patch.

The compiler seems to drop the function if compiled with lto.
Don't know if this is the issue of gcc or this specific function. That's why I don't try to upstreaming this patch. If someone understands better why this happens this person should do it instead