ansible: mask systemd-binfmt service on qemu-user-static install (#145)

systemd-binfmt service [1], provided by systemd Ubuntu package [2] is
in conflict with our custom one-shot qemu-user-static service.

Recently an automated update of python3.12 on s390x BPF CI hosts
triggered a restart of systemd-binfmt, which broke the test runners.

Masking systemd-binfmt service shoud prevent similar runner failures
in the future.

Ideally we'd want to switch to systemd-binfmt. However currently it
doesn't work for us: on s390x qemu segfaults with standard
qemu-user-static binaries, as opposed to qus [3] container we're
currently using.

[1]: https://www.freedesktop.org/software/systemd/man/latest/systemd-binfmt.service.html
[2]: https://manpages.ubuntu.com/manpages/noble/man8/systemd-binfmt.service.8.html
[3]: https://github.com/dbhi/qus

ansible/roles/qemu-user-static/tasks/main.yml

@@ -23,6 +23,13 @@
     group: root
   register: qemu_user_static
 
+- name: Mask systemd-binfmt service
+  become: true
+  systemd:
+    name: systemd-binfmt
+    state: stopped
+    masked: yes
+
 # Building the image relies on this having started. Force starting the service when this file changes.
 - name: start qemu-user-static
   become: yes