src/Doc/Intro/document/build

proper priority for error over warning, which got mixed up in 0546e036d1c0 and 4df2727a0b5f;

#!/usr/bin/env bash

set -e

FORMAT="$1"
VARIANT="$2"

"$ISABELLE_TOOL" logo
"$ISABELLE_HOME/src/Doc/prepare_document" "$FORMAT"