tests/test-dirstate-nonnormalset.t

tests: stabilize test-persistent-nodemap.t on Windows

Several issues here:

  - Hooks can't invoke shell scripts on Windows, so use `sh` to launch
  - `dd` in MSYS only recognizes `status=noxfer`
  - The `PATH` updating triggered a massive slowdown, but is no longer needed

I have no idea why, but removing the `PATH` update substantially increased the
speed of the test.  It was running finishing at ~4:30 with `--debug` and ~14:50
without it, but now completes in ~2:20 on my Windows laptop.

Differential Revision: https://phab.mercurial-scm.org/D10636

  $ cat >> $HGRCPATH << EOF
  > [command-templates]
  > log="{rev}:{node|short} ({phase}) [{tags} {bookmarks}] {desc|firstline}\n"
  > [extensions]
  > dirstateparanoidcheck = $TESTDIR/../contrib/dirstatenonnormalcheck.py
  > [experimental]
  > nonnormalparanoidcheck = True
  > [devel]
  > all-warnings=True
  > EOF
  $ mkcommit() {
  >    echo "$1" > "$1"
  >    hg add "$1"
  >    hg ci -m "add $1"
  > }

  $ hg init testrepo
  $ cd testrepo
  $ mkcommit a
  $ mkcommit b
  $ mkcommit c
  $ hg status