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