Allow two bits for libunw_failed, since a recent change has it taking on three possible values (-1, 0, 1).
Allow two bits for libunw_failed, since a recent change has it taking
on three possible values (-1, 0, 1).

HPCToolkit/hpctoolkit,HPCToolkit/hpctoolkit,HPCToolkit/hpctoolkit,HPCToolkit/hpctoolkit,HPCToolkit/hpctoolkit,HPCToolkit/hpctoolkit