On FreeBSD (and possibly Linux) using `inotify-tools`:

Given:

```
{:ok, pid} = FileSystem.start_link(dirs: ["/path/to/some/files"])
```

Results in the error:

```
Couldn't watch modify: No such file or directory
````

This is similar to executing `inotifywait modify` at the console.

This fix ensures arguments to 'sh' are passed properly.