lib/Tools/dotnet

clarified output;

#!/usr/bin/env bash
#
# Author: Makarius
#
# DESCRIPTION: invoke the dotnet CLI driver within the Isabelle environment

if [ -z "$ISABELLE_DOTNET" ]; then
  echo "Missing dotnet installation: need to run \"isabelle dotnet_setup\" first" >&2
  exit 2
else
  exec "$ISABELLE_DOTNET" "$@"
fi