docs: document how to get SPICE clipboard sharing to working on NixOS

[genevieve-me]

Expected behaviour

When "options / automatic clipboard sharing" is checked, it should be possible to copy on the host and paste into the guest.

Actual behaviour

Unable to get any sort of clipboard sharing in either direction.

Steps to reproduce the behaviour

• quickget fedora 39 KDE
• quickemu --vm fedora-39-KDE.conf
• Install Fedora with default settings in guest.
• Reboot, apply system update in guest. Install spice-vdagent (dnf install spice-vdagent) in guest. Shutdown.
• quickemu --vm fedora-39-KDE.conf --display spice in host.
• Tried in both Wayland and X11 environments in the guest. Only tried in a Wayland host environment, so it's possible that's where the issue lies.

Quickemu output

Run quickemu or quickget and paste the output here.

genevieve ~ > quickemu

Usage
  .quickemu-wrapped --vm ubuntu.conf

You can also pass optional parameters
...

Linux Distribution & Kernel

Linux godard 6.1.75 #1-NixOS SMP PREEMPT_DYNAMIC Thu Jan 25 23:27:52 UTC 2024 x86_64 GNU/Linux

Running sway 1.9 (source build), nothing installed that would affect the clipboard

[flexiondotorg]

I've added a section to the wiki which describe how to enable clipboard sharing and includes details for NixOS.

• https://github.com/quickemu-project/quickemu/wiki/05-Advanced-quickemu-configuration#clipboard-sharing

[name-snrl]

@flexiondotorg I think it would be great for me to also write about how this doesn't work for wayland and what workarounds can be used for it.

https://gitlab.freedesktop.org/spice/linux/vd_agent/-/issues/26
https://github.com/name-snrl/nixos-configuration/blob/e29a7d45ed8dce5c82189e858c2d97c3fa895458/modules/nixos/profiles/system/vm-config.nix#L37-L47