manual/build/buildone.sh: redirect xsltproc's stderr to stdout

xsltproc sends informational messages like "writing out chapter X" to stderr.
For automatic building with stdout redirected to /dev/null we don't want to see
them.  Obviously this also means that errors will not be logged properly in
the cron mail and xsltproc will just return with non-zero exit status.

In theory we'd want to filter out those "Writing out" lines on stderr instead.

0 files changed, 0 insertions, 0 deletions