Try to fix macOS bursting bubbles issue

[fantix]

When creating a new instance on macOS, sometimes lots of bubble notifications show up at once. I'm not able to reliably reproduce the issue, so this is a guessed fix trying to avoid libc::mkdir("~/Library/LaunchAgents", ...) if unnecessary.

See also #1054

[mmastrac]

I have a feeling this won't help. The extra mkdir is likely just erroring out without performing any modifications -- the underlying cause appears to be a background launch agent database that gets corrupted:

https://discussions.apple.com/thread/254341579?sortBy=rank

sfltool resetbtm is apparently the way to fix this.

We could still land this as it's probably harmless either way.