Ben Gamari authored May 13, 2018 and Ben Gamari committed May 13, 2018

This fixes #15021 using a the same approach as was used to fix the issue
in ghc (#10762).

Test Plan: Validate on Windows as user whose username contains
non-ASCII characters

Reviewers: simonmar

Reviewed By: simonmar

Subscribers: lehins, thomie, carter

GHC Trac Issues: #15021

Differential Revision: https://phabricator.haskell.org/D4642