message: make sure LIBTORRENT_REVISION is set
diff: @@ -77,6 +77,7 @@ function build_openssl {
  function prepare_libtorrent {
  abort_if_var_unset "SRC" ${SRC}
  abort_if_var_unset "LIBTORRENT_ROOT" ${LIBTORRENT_ROOT}
  + abort_if_var_unset "LIBTORRENT_REVISION" ${LIBTORRENT_REVISION}
  if [ ! -d ${LIBTORRENT_ROOT} ]; then
  pushd ${SRC}
  