Automatically generate rule file list for TeaVM

[razzolini]

When running on the JVM, the program finds rule files by listing the contents of a predetermined directory (rules/).
However, on TeaVM, the file API doesn't support the listing of directory contents, so the program reads a rules.list file, which contains the paths of all rule files to load.
Currently, this file has to be written manually, but it would be better to generate it automatically when building for TeaVM.