don't complain about missing include()s during cumulative evaluation

it produces simply too many false positives.

Change-Id: I3dfa109866450babe5c16f84665ad22024d99e42
Reviewed-by: Joerg Bornemann <joerg.bornemann@digia.com>
(cherry picked from qttools/08bae158320f6d73bf44fcf43f45f51a01334544)

src/shared/proparser/qmakebuiltins.cpp

@@ -1265,6 +1265,8 @@ QMakeEvaluator::VisitReturn QMakeEvaluator::evaluateBuiltinConditional(
         }
         QString parseInto;
         LoadFlags flags = 0;
+        if (m_cumulative)
+            flags = LoadSilent;
         if (args.count() >= 2) {
             parseInto = args.at(1).toQString(m_tmp2);
             if (args.count() >= 3 && isTrue(args.at(2), m_tmp3))