src/Tools/JVM/java_ext_dirs

added helper -- cf. SET616^5

#!/usr/bin/env bash
#
# Author: Makarius
#
# Augment Java extension directories.

## diagnostics

function fail()
{
  echo "$1" >&2
  exit 2
}

[ -n "$ISABELLE_HOME" ] || fail "Missing Isabelle settings environment"


## main

isabelle_jdk java \
  -classpath "$(jvmpath "$ISABELLE_HOME/src/Tools/JVM/java_ext_dirs.jar")" \
  isabelle.Java_Ext_Dirs "$(jvmpath "$ISABELLE_HOME/lib/classes/ext")" 2>/dev/null