Motivation for this change

libvirtd requires qemu-img to manage disk images.

If qemu-img is not found by libvirtd, attempting to create a qcow2 image fails with this error:

$ cat >/tmp/vol.xml <<EOF
<volume>
  <name>test</name>
  <capacity>1000</capacity>
  <target>
    <format type="qcow2"/>
  </target>
</volume>
EOF
$ virsh -c qemu:///system vol-create --pool default --file /tmp/vol.xml
error: Failed to create vol from /tmp/vol.xml
error: internal error: creation of non-raw file images is not supported without qemu-img.

Things done

• Tested using sandboxing (nix.useSandbox on NixOS, or option build-use-sandbox in nix.conf on non-NixOS)
• Built on platform(s)
  • NixOS
  • macOS
  • other Linux distributions
• Tested via one or more NixOS test(s) if existing and applicable for the change (look inside nixos/tests)
• Tested compilation of all pkgs that depend on this change using nix-shell -p nox --run "nox-review wip"
• Tested execution of all binary files (usually in ./result/bin/)
• Fits CONTRIBUTING.md.