How about

    {
      \key ces \major
      \bar ".|:"
      \grace \tweak extra-spacing-width #'(-1 . 0) as'8 \glissando
      ces''2
    }
or

    {
      \key ces \major
      \temporary\override Staff.BarLine.space-alist.first-note = #'(fixed-space . 6)
      \bar ".|:"
      \grace as'8 \glissando
      \revert Staff.BarLine.space-alist.first-note
      ces''2
    }