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/gitlab_runner/files/libvirt-executor

@@ -78,7 +78,6 @@ create_vm_template() {
   ssh pacman -Sy --noconfirm --needed archlinux-keyring
   ssh pacman -Syu --noconfirm git git-lfs gitlab-runner
   ssh "sed -E 's/^#(IgnorePkg *=)/\1 linux/' -i /etc/pacman.conf"
-  ssh rm /etc/machine-id /var/lib/dbus/machine-id
 
   # Reboot to be sure the network is working
   virsh shutdown "${vm_name}"
@@ -86,6 +85,7 @@ create_vm_template() {
   virsh start "${vm_name}"
   vm_ip=""
   wait_for_ssh "${vm_name}"
+  ssh rm /etc/machine-id /var/lib/dbus/machine-id
 
   virsh shutdown "${vm_name}"
   wait_for_vm_shutdown "${vm_name}"
@@ -112,7 +112,7 @@ prepare() {
 run() {
   vm_name="$(get_vm_name)"
   wait_for_ssh "${vm_name}"
-  if [[ "${2:-}" =~ upload_artifacts_.* ]]; then
+  if [[ "${2:-}" == 'upload_artifacts_'* ]]; then
     ssh 'TMPDIR=/var/tmp bash' < "${1}" || exit "${BUILD_FAILURE_EXIT_CODE:-1}"
   else
     ssh bash < "${1}" || exit "${BUILD_FAILURE_EXIT_CODE:-1}"