xcode12: fix compiler warnings
xcode12: fix compiler warnings

Clang says: "loop variable 'xxx' is always a copy because the range of
type 'QJsonArray' does not return a reference [-Wrange-loop-analysis]"

Change-Id: Ibb33f077dfaaf635300f6c75f6684d4a3d7632de
Reviewed-by: Christian Kandeler <3aa99dcdd3f0cac61fb81c2a11771c0cc2497607@qt.io>

qtproject/qt-labs-qbs,qt-labs/qbs,qt-labs/qbs,qt-labs/qbs,qtproject/qt-labs-qbs,qt-labs/qbs,qtproject/qt-labs-qbs,qtproject/qt-labs-qbs,qt-labs/qbs,qt-labs/qbs,qtproject/qt-labs-qbs,qtproject/qt-labs-qbs,qt-labs/qbs,qtproject/qt-labs-qbs