more robust startup, notably on Ubuntu 24.04 with its strict policies on the "chrome-sandbox" executable;
#!/usr/bin/env bash
#
# Author: Makarius
#
# DESCRIPTION: setup OCaml base compiler via OPAM
set -e
if [ -d "$ISABELLE_OPAM_ROOT/$ISABELLE_OCAML_VERSION/bin" ]
then
isabelle_opam switch -y "$ISABELLE_OCAML_VERSION"
elif [ -e "$ISABELLE_OPAM_ROOT/config" ]
then
isabelle_opam switch create -y "$ISABELLE_OCAML_VERSION"
else
mkdir -p "$ISABELLE_OPAM_ROOT"
cd "$ISABELLE_OPAM_ROOT"
isabelle_opam init -y --disable-sandboxing --no-setup --compiler="$ISABELLE_OCAML_VERSION"
fi