qmake: Run the test version of system()

... also when PROEVALUATOR_FULL is not defined.
For more correct parsing. We do not believe that this introduces
additional risk, because the replace version of system() has always been
enabled, and appears to be used more often.

Fixes: QTCREATORBUG-23940
Change-Id: I036a20fdab3f6c51c612912b60686a123440f397
Reviewed-by: Joerg Bornemann <joerg.bornemann@qt.io>

src/shared/proparser/qmakebuiltins.cpp

@@ -1742,7 +1742,6 @@ QMakeEvaluator::VisitReturn QMakeEvaluator::evaluateBuiltinConditional(
             evalError(fL1S("system(exec) requires one argument."));
             return ReturnFalse;
         }
-#ifdef PROEVALUATOR_FULL
         if (m_cumulative) // Anything else would be insanity
             return ReturnFalse;
 #ifndef QT_BOOTSTRAPPED
@@ -1759,9 +1758,6 @@ QMakeEvaluator::VisitReturn QMakeEvaluator::evaluateBuiltinConditional(
             raise(WTERMSIG(ec));
 #  endif
         return returnBool(ec == 0);
-#endif
-#else
-        return ReturnTrue;
 #endif
     }
     case T_ISEMPTY: {