avoid spurious error messages, e.g. when scala is missing;
#!/usr/bin/env bash
#
# Author: Makarius
#
# Invoke ghc via "stack".
if [ -f "$ISABELLE_STACK_ROOT/ISABELLE_GHC_EXE-$ISABELLE_PLATFORM_FAMILY" ]
then
isabelle_stack ghc -- "$@"
else
echo "Cannot execute ghc: missing Isabelle GHC setup" >&2
exit 127
fi