This creates one .cmi and one .cmo file with the same basename as the file to check. I use `source` so the files will appear somewhere in /tmp. I presumend these are in a temporary folder and deleted by Flycheck afterwards. It also creates an `a.out` file, but I will add the `-c` option to suppress that.

The `-i` option does not generate any files, but will print all defined values in addition to the warnings, i.e., there would be output without any warnings / errors.