A hosted runner of the ubuntu-24.04 pool is not promised nested virtualization, and
3 of the 16 suites of run 42182554717 failed the check of /dev/kvm. rerun-no-kvm.yaml
could not help: a workflow_run workflow runs only from the default branch, where the
file is not, and a run cannot rerun its own failed jobs while it is in progress.
The step "Enable KVM" of the nix action is now the only one that enables KVM
(enable_kvm of install-nix-action is off), runs before the disk and the install,
waits for udev to settle and polls /dev/kvm for 30 seconds instead of testing it
once, 42 ms after an asynchronous udevadm trigger, and prints what tells a missing
device from a rule that was not applied yet. With defer-no-kvm a host without KVM
is an output, not a failure.
_vm.yaml calls _vm-attempt.yaml up to three times: the suites that found no KVM are
listed through the artifacts of the run and run again on new machines, and the last
attempt fails them. vm-fast and vm-slow are calls of it. rerun-no-kvm.yaml is
removed.
