One modern and portable way is to use Node.js. Have a look in the Extras -> Node For Max Overview -> File System. It should work in js too. Or there is this, in Java. And probably many other solutions…

shell and then rmdir on Mac or RD on windows

Thank you @PDELGES and @SOURCE AUDIO. I'm already using the NodeJS solution; a C API function was what I was looking for. (Windows RemoveDirectory() from "fileapi.h" cannot be used). Meanwhile, J. Bernstein informed in the facebook group that no API function for that was made available.