art_make() on a directory with only modules fails
If you run art_make() [no arguments] on a directory that only has modules (no non-module code), CMake fails with a incorrect number of arguments error.
"art_make()" has no library dependencies (the modules obviously can't do much, but they are just educational), so the art_liblist variable is never set. Later in the code, _art_simple_plugin is called, but this requires the liblist argument, which is undefined. Hence the error.
At the top of art_make, just below "set (art_file_list ""), add "set(art_liblist FALSE)". If LIBRARIES is passed in, then they will replace FALSE. If not, then FALSE is passed as the liblist to _art_simple_plugin and eventually to simple_plugin where FALSE causes the if statement regarding the liblist to be false and so it correctly does not run its body.