Add QT_NO_NARROWING_CONVERSIONS_IN_CONNECT as default compile flags

Summary: Use QT_NO_NARROWING_CONVERSIONS_IN_CONNECT as default flags

Reviewers: dfaure

Reviewed By: dfaure

Subscribers: kde-frameworks-devel, kde-buildsystem

Tags: Frameworks, Build System

Differential Revision: https://phabricator.kde.org/D15566