Update xhpast.exe

Summary:
Fixes T4592. I think I got this working. Rough steps were:

  - Install mingw
  - Install git + git bash
  - Using mingw shell //only//, run build script
  - Oh you have to muck with PATH a lot
  - why is it hanging
  - I wish I could paste
  - this looks like a `.exe`

Test Plan: ???

Reviewers: richardvanvelzen

Reviewed By: richardvanvelzen

Subscribers: epriestley

Maniphest Tasks: T4592

Differential Revision: https://secure.phabricator.com/D9378