No information on RG350/OpenDingux devices on guides/generating-retroarch-logs

[john-parton]

Describe the bug
The "Generating Logs" page doesn't include instructions for RG350 and OpenDingux-based devices. https://docs.libretro.com/guides/generating-retroarch-logs/

Expected behavior/changes
The RG350 and OpenDingux builds are quite different from the other builds, and I'm having a very hard time getting DEBUG logs to show up. I went to that page for information and there wasn't any. It would be nice if there were info on how to do this.

Additional context
I'm currently trying to get dosbox-pure to compile for the RG350, and the lowest log level that it seems to output is INFO which makes debugging very difficult.

[john-parton]

Here's a PR that just adds a "there are no docs" paragraph: #571