fix FS watcher for linux

[LilithSilver]

fixes #154

[wjt]

I tested this with moddable-platformer on Linux (namely Bluefin 43). The log spam from #154 is gone. The idle CPU usage has gone from busylooping to ~5%.

I edited a file externally (namely README.md) - the change appeared in the Patchwork sidebar immediately.

One thing I can't explain: on the branch I created to test this PR, when I select no revision in the sidebar, this huge number of changes is shown:

Now I have hit Ctrl+s with main.tscn open and it has vanished, in favour of an apparently empty change to main.tscn:

Odd but I have no evidence it is related.

[LilithSilver]

I imagine this is unrelated. I'm unable to repro on Windows. Are you able to consistently repro on this PR but not main?

If so, I'll spin up a linux machine and see if I can repro it.

If not, go ahead and open another issue and I'll merge this PR!

Note that empty diffs sometimes show up with project upgrades. Since we're now on Godot 4.7, main.tscn is likely to have some nothing-changes caused by resaving, if this was your first time saving the scene in this version. That definitely doesn't explain the first, absolutely-not-empty diff, though! That's weird.

[wjt]

I reproduced the same issue with main so it is unrelated to this PR. I will file a separate issue.