luamin option to preserve newlines
Luamin replaces all non-significant whitespace with single space characters. This causes minified programs to be on a single line according to Pico-8, such as in error messages. It would cost nothing and make error messages more useful if it used a newline instead of a space if a block of whitespace contains at least one newline.

It looks like it's supposed to be doing this but there's at least one report of minified code being on a single line.