D329: setup: Fix installing in a mingw environment

[glandium (Mike Hommey)]

glandium added a comment.


  4.3.1 can't currently be installed with MINGW64 python currently because of this, so I'd say yes.

REPOSITORY
  rHG Mercurial

REVISION DETAIL
  https://phab.mercurial-scm.org/D329

To: glandium, #hg-reviewers, quark
Cc: durin42, mercurial-devel