bug#53463: ci.guix.gnu.org not building the 'guix' job

[Mathieu Othacehe <othacehe@gnu.org>]

Hey,

> Oh!  That indicates that it’s failing to offload to one of the
> ‘localhost’ build machines specified in /etc/guix/machines.scm.
> Normally there’s an SSH tunnel set up for those, but I guess it broke.
>
> Perhaps we can update /etc/guix/machines.scm to refer to armhf-linux
> machines by their WireGuard IP?

Seems like the right thing to do. This bit is also an unstaged change in
the berlin maintenance repository, we should commit it. Tobias, could
you have a look :) ?

--8<---------------cut here---------------start------------->8---
+(define powerpc64le
+  (list
+   ;; A VM donated/hosted by OSUOSL & administered by nckx.
+   ;; XXX: SSH tunnel via overdrive1:
+   ;; ssh -L 2224:p9.tobias.gr:22 hydra@10.0.0.3
+   #;(build-machine
+    ;;(name "p9.tobias.gr")
+    (name "localhost")
+    (port 2224)
+    (user "hydra")
+    (systems '("powerpc64le-linux"))
+    (host-key "ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIJEbRxJ6WqnNLYEMNDUKFcdMtyZ9V/6oEfBFSHY8xE6A nckx"))))
--8<---------------cut here---------------end--------------->8---

I also found that other machines were unreachable and commented them:

--8<---------------cut here---------------start------------->8---
   ;; CPU: 16 ARM Cortex-A72 cores
   ;; RAM: 32 GB
-  (list (build-machine
+  (list #;(build-machine
          ;;kreuzberg
          (name "10.0.0.9")
          (user "hydra")
@@ -243,13 +256,13 @@
    ;; BeagleBoard X15 kindly hosted by Simon Josefsson.
    ;; CPU: Cortex A15 (2 cores)
    ;; RAM: 2 GB
-   (build-machine
+   #;(build-machine
     (name "10.0.0.5")                   ;guix-x15
     (user "hydra")
     (systems '("armhf-linux"))
     (host-key "ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIOfXjwCAFWeGiUoOVXEgtIeXxbtymjOTg7ph1ObMAcJ0 root@beaglebone"))
 
-   (build-machine
+   #;(build-machine
     (name "10.0.0.6")                   ;guix-x15b
     (user "hydra")
     (systems '("armhf-linux"))
--8<---------------cut here---------------end--------------->8---

Nevertheless we are hitting an offload issue here, maybe an occurrence
of #24496. The offload mechanism should timeout when a machine is
unreachable instead of retrying over and over, causing all evaluation
processes to hang.

Thanks,

Mathieu