fix: add check before remove output.img and add debug output

[meteyou]

This PR introduces a conditional check before attempting to remove output.img, along with a corresponding warning message. This change prevents unnecessary error logs when the file doesn't exist. The issue was a minor annoyance in my GitHub workflow logs, and this fix ensures a cleaner output.

• Old log (with error)
• New log (error resolved)

FYI: I hadn't tested it with log, because I only tested it in my GitHub workflow and there is no output.img. I can just add a step to create a file, if needed.

[foosel]

Good point!

But I think we don't really need a warming here, so just something like

[ -f "output.img" ] && rm -f "output.img"

would be even better (and actually reflect what I intended there 😅)

[meteyou]

Thanks for the feedback! no problem, I have updated the PR.