Fix build and boot errors on NixOS 21.11

[ilian]

Fix building the nix module and error while booting the VM on NixOS 21.11.

Trying to run 2 VMs at a time still results in the following error though:

2021/12/20 11:59:28 internal error: process exited while connecting to monitor: qemu-system-x86_64: -fsdev local,security_model=passthrough,id=fsdev-fs0,path=/nix/store,readonly: warning: short-form boolean option 'readonly' deprecated
Please use readonly=on instead
2021-12-20T10:59:28.668638Z qemu-system-x86_64: -blockdev {"node-name":"libvirt-1-format","read-only":false,"cache":{"direct":false,"no-flush":false},"driver":"qcow2","file":"libvirt-1-storage","backing":null}: Failed to get "write" lock
Is another process using the image [/home/ilian/appvm/.fake.qcow2]?

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• [x] I tested it locally.
• [x] I tried to run at least one application VM and it works.

[jollheef]

Hello,

Thank you.

Trying to run 2 VMs at a time still results in the following error though

Fixed in 84374314a29345f0cbd47febe2ab7d529e13246a