buildFHSEnvBubblewrap: extraPreBwrapCmds after variable initialisation (#344404)

  indentLines = str: concatLines (map (s: "  " + s) (filter (s: s != "") (splitString "\n" str)));

  bwrapCmd = { initArgs ? "" }: ''

    ${extraPreBwrapCmds}

    ignored=(/nix /dev /proc /etc ${optionalString privateTmp "/tmp"})

    ro_mounts=()

    symlinks=()

    etc_ignored=()

    ${extraPreBwrapCmds}

    # loop through all entries of root in the fhs environment, except its /etc.

    for i in ${fhsenv}/*; do

      path="/''${i##*/}"