[plugin-logging] Crash if there is a log file without write permission

If I configure to write logs to a file and I don't have write permission to that file, my tauri application crashes.

For example, if I open the application with sudo and then open it without sudo.

```
tauri_plugin_log::Builder::new()
.target(tauri_plugin_log::Target::new(
tauri_plugin_log::TargetKind::LogDir {
file_name: Some("logs".to_string()),
},
))
.build()
```