allow to switch ISABELLE_OCAML_VERSION later on;
simplified command-line: no user args;
#!/usr/bin/env bash
#
# Author: Makarius
#
# DESCRIPTION: OCaml setup via OPAM
if [ -d "$ISABELLE_OPAM_ROOT" ]
then
isabelle_opam switch "$ISABELLE_OCAML_VERSION"
else
isabelle_opam init --no-setup --compiler="$ISABELLE_OCAML_VERSION"
fi