In order to build the xlc compiler, you need to install Maven first. Visit this page for the Maven installation instructions.
After this, you can build the compiler jar file (xlc.jar), just with the make command.
For compiling an XFSM Language file, to obtain the JSON representation of the XFSM, you need to use the command
java -jar xlc.jar -i input_file.xl -o output_file.json