gitlab_runner: Add VM based executor (libvirt-executor)

For some workloads running in a container is too restrictive, ex:
arch-boxes (loop device, filesystem mount, pacstrap) and archiso
(pacstrap). Currently they both run a TCG accelerated QEMU VM, which is
very slow and painful to work with. We should provide a better option to
our users!

This adds a hardware accelerated VM for this kinds of workloads, which
is way faster and you can do whatever you like (mostly)!

Fix #283

---

TODO:

• Enable KSM?
• Get archiso to build
  • Done: https://gitlab.archlinux.org/klausenbusk/archiso/-/pipelines/10976
• Use BUILD_FAILURE_EXIT_CODE and SYSTEM_FAILURE_EXIT_CODE: https://docs.gitlab.com/runner/executors/custom.html#error-handling
• Fix existing users to use the secure-vm tag

roles/libvirt/tasks/main.yml

@@ -7,36 +7,9 @@
   pacman: name=virt-install state=present
 
   # bridge-utils?
-  # TODO: autostart network
-  # reload firewalld for at få libvirt zonen
-  # cpu model host?
 
 - name: autostart default network on boot
   file: src=/etc/libvirt/qemu/networks/default.xml dest=/etc/libvirt/qemu/networks/autostart/default.xml state=link owner=root group=root
 
-- name: install loki configuration
-  copy: src=loki.yaml dest=/etc/loki/ owner=root group=root mode=0644
-  notify: restart loki
-
-- name: install python-passlib
-  pacman: name=python-passlib
-
-- name: create htpasswd for nginx loki endpoint
-  htpasswd:
-    path: "{{ loki_nginx_htpasswd }}"
-    name: "{{ vault_loki_nginx_user }}"
-    password: "{{ vault_loki_nginx_passwd }}"
-    owner: root
-    group: http
-    mode: 0640
-
-- name: make nginx log dir
-  file: path=/var/log/nginx/{{ logging_domain }} state=directory owner=root group=root mode=0755
-
-- name: set up nginx
-  template: src=nginx.d.conf.j2 dest="/etc/nginx/nginx.d/logging.conf" owner=root group=root mode=644
-  notify: reload nginx
-  tags: ['nginx']
-
 - name: start and enable libvirtd
   systemd: name=libvirtd.service enabled=yes daemon_reload=yes state=started