Support xsel

I keep getting the following error message when I try to use the clipboard: "Couldn't find the required `xsel` binary. On Debian/Ubuntu you can install it with; sudo apt install xsel". I do have xsel installed, so I think this might be a flatpak issue?

I am running VSCode purely in wayland using ozone, in case that might have anything to do with it.

Let me know if I can do anything to help solve the issue, or if any more information is needed.

No source files or tests are named. Start by reproducing clipboard use in the Flatpak under Wayland with xsel installed, then inspect the packaging and runtime configuration; done means the cause is identified and the behavior has a verified resolution or clearly documented limitation.

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