[Backport release-21.05] qemu, runInLinuxVM: fix KVM availability check#148029

alyssais merged 2 commits intoNixOS:release-21.05NixOS/nixpkgs:release-21.05from

mschwaig:backport-125948-to-release-21.05mschwaig/nixpkgs:backport-125948-to-release-21.05Copy head branch name to clipboard