Add missing Import Env Variable
Summary:
Without this, in Qt 5.14 I get an android-like QQC2 theme
This used to work on Qt 5.13 so I assume that it's a regression
Reviewers: mart
Reviewed By: mart
Subscribers: apol, davidedmundson, kde-frameworks-devel, kde-buildsystem
Tags: Frameworks, Build System
Differential Revision: https://phabricator.kde.org/D26573