wenzelm [Mon, 11 Oct 2021 17:04:35 +0200] rev 74499
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;