It seems to have a thing for .jar, it looks like it is replacing .jar anywhere in the absolute current working directory with -jar which then shoots itself in the foot and causes FileNotFound

pwd && java -jar jandex-1.1.0.Final.jar -v my-ejb-interceptors.jar

/home/bmaxwell/work/source/git/jandex/target/bmaxwell-jandex-tests/test/test.jar

java.io.FileNotFoundException: /home/bmaxwell/work/source/git/jandex/target/bmaxwell-jandex-tests/test/test-jar/my-ejb-interceptors-jar.idx (No such file or directory)
at java.io.FileOutputStream.open(Native Method)
at java.io.FileOutputStream.<init>(FileOutputStream.java:194)
at java.io.FileOutputStream.<init>(FileOutputStream.java:145)
at org.jboss.jandex.JarIndexer.createJarIndex(JarIndexer.java:102)
at org.jboss.jandex.JarIndexer.createJarIndex(JarIndexer.java:66)
at org.jboss.jandex.Main.execute(Main.java:69)
at org.jboss.jandex.Main.main(Main.java:52)