Inspired by this answer, I\'m using:
java -jar %BUILDTOOLSPATH%\\jill.jar --output classes.jayce src
java -jar %BUILDTOOLSPATH%\\jack.jar --import classes.jayce
Seems like you're stuck with the folder browsing structure. Its different for Linux/Unix based systems and Windows. Windows use backward slash to separate directories in file path, where as linux uses forward slash for the same.
Referring this link
In Windows, backslashes are used to separate directories in file paths (ex: C:\Program Files\Common Files\microsoft shared). On Mac and Unix systems, forward slashes are used for the same purpose (ex: /System/Library/Screen Savers).
The guide you referred is Linux/Unix based. So the solution to your question is that wherever you find some file getting accessed by file path, simply replace the forward slash with backward slash and that should solve this problem.