hydra: Adjust offload setup for childhurds.

This is a followup to ae20c49e0b.

* hydra/machines-for-berlin.scm (template-x86_64): Add case for
‘childhurd-ip?’ when defining ‘systems’ field.
(x86_64->childhurd): Remove.
<top level>: Adjust accordingly.

hydra/machines-for-berlin.scm

@@ -157,7 +157,13 @@
      (build-machine
       (name ip)
       (user "hydra")
-      (systems '("x86_64-linux" "i686-linux"))
+      (systems
+       ;; Some of these machines run a childhurd, which they offload to (we
+       ;; effectively have two-level offloading, then).
+       (append (if (childhurd-ip? ip)
+                   '("i586-gnu")
+                   '())
+               '("x86_64-linux" "i686-linux")))
       (host-key key)
       (compression "no")
       (speed 2)
@@ -184,14 +190,6 @@
    (speed .9)
    (parallel-builds 1)))
 
-(define (x86_64->childhurd machine)
-  (build-machine
-   (inherit machine)
-   (systems '("i586-gnu"))
-   (host-key "ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIMMrm7dgMwQnsUcP//JW7odl1z632urrew036qcqbxc4 root@berlin.guix.gnu.org")
-   (port 10022)
-   (parallel-builds 1)))
-
 (define overdrive
   ;; The SoftIron OverDrive 1000 donated by ARM:
   ;; CPU: AMD A1100 (4 Cortex A57 cores)
@@ -330,16 +328,7 @@
   (member ip '("141.80.167.158" "141.80.167.159"
                "141.80.167.160" "141.80.167.161")))
 
-(let* ((x86_64 (map template-x86_64 hosts))
-       (fast   (filter-map
-                (match-lambda
-                  ((name key 128)
-                   (find (lambda (machine)
-                           (string=? (build-machine-name machine) name))
-                         x86_64))
-                  (_ #f))
-                hosts))
-       (fast/hurd (filter (compose childhurd-ip? build-machine-name) fast)))
+(let* ((x86_64 (map template-x86_64 hosts)))
   (append overdrive
           honeycomb
           ;; This has been disabled until bug# 43513 is fixed.
@@ -349,4 +338,4 @@
           x86_64
           ;; This has been disabled until bug# 43513 is fixed.
           ;;(map x86_64->qemu-armhf fast)
-          (map x86_64->childhurd fast/hurd)))
+          ))