Fix qmakeproject unittest to work on Windows.
Summary: Fix qmakeproject unittest to work on Windows
Test Plan: Build on Windows, verify test passes. Build on Linux, verify test passes (as before).
Reviewers: KDevelop, kfunk
Reviewed By: KDevelop, kfunk
Subscribers: kdevelop-devel
Tags: KDevelop
Differential Revision: https://phabricator.kde.org/D17158