Add vmm-xen-unified to example configs

But don't build it by default, as it requires extra setup (signing keys
specifically).

QubesOS/qubes-issues#8206

Author: marmarek

example-configs/qubes-os-main.yml

@@ -91,6 +91,9 @@ components:
       url: https://github.com/QubesOS/qubes-linux-kernel
       branch: main
       timeout: 21600
+  - vmm-xen-unified:
+      # requires extra setup for signing, disable by default
+      packages: false
   - artwork
   - grub2
   - grub2-theme

example-configs/qubes-os-r4.3.yml

@@ -88,6 +88,9 @@ components:
       url: https://github.com/QubesOS/qubes-linux-kernel
       branch: main
       timeout: 21600
+  - vmm-xen-unified:
+      # requires extra setup for signing, disable by default
+      packages: false
   - artwork
   - grub2
   - grub2-theme