std.fs: Fix `WalkerEntry.dir` not always being the containing dir

Before this commit, the modified test would fail with `FileNotFound` because the `entry.dir` would be for the entry itself rather than the containing dir of the entry. That is, if you were walking a tree of `a/b`, then (previously) the entry for `b` would incorrectly have an `entry.dir` for `b` rather than `a`.
764cf4e53fRyan Liptak committed on 8/15/2022, 8:25:51 AM· committed by Veikka Tuominenparent2279f27
2 files changedLine totals unavailable