t\rt-84767.t fails with MSVC built perl due to dir separator

Hard coded directory separator causes comparison to fail:

    Failed test 'die with input line number'
    t\rt-84767.t ............... 1/1 #   at t\rt-84767.t line 21.
                    'error at t\rt-84767.t line 19.
    '
    doesn't match '(?^:at t/rt-84767.t line 19)'

Fix by using `\Q$0\E` instead of `t/$Script`.
Merge pull request #160 from nanis/nanis-fix-t-rt-84767

t\rt-84767.t fails with MSVC built perl due to dir separator