workaround for old macOS versions, after change of Let's Encrypt root certificate --- see also https://letsencrypt.org/docs/dst-root-ca-x3-expiration-september-2021 --- Java/Scala Isabelle_System.download() works, but curl doens't;
#!/usr/bin/env bash
#
# Author: Makarius
#
# DESCRIPTION: invoke Scala compiler within the Isabelle environment
isabelle scala_build || exit $?
classpath "$ISABELLE_SETUP_CLASSPATH"; unset ISABELLE_SETUP_CLASSPATH
classpath "$CLASSPATH"; unset CLASSPATH
isabelle_scala scalac -Dfile.encoding=UTF-8 \
-classpath "$(platform_path "$ISABELLE_CLASSPATH")" "$@"