Jandex fails with NPE on Java 21

[tomas-langer]

Also build tool uses an older version that incorrectly tries to rebuild a newer index.

Stacktrace:

Caused by: java.lang.NullPointerException: Cannot read the array length because "bytes" is null
    at org.jboss.jandex.IndexWriterV2.writeByteTable (IndexWriterV2.java:228)
    at org.jboss.jandex.IndexWriterV2.write (IndexWriterV2.java:194)
    at org.jboss.jandex.IndexWriter.write (IndexWriter.java:107)
    at org.jboss.jandex.IndexWriter.write (IndexWriter.java:74)
    at io.helidon.build.linker.Jar.addIndex (Jar.java:567)
    at io.helidon.build.linker.Jar.copy (Jar.java:503)
    at io.helidon.build.linker.Jar.copyToDirectory (Jar.java:364)
    at io.helidon.build.linker.Application.lambda$install$1 (Application.java:102)

Related to helidon-io/helidon#7221