don't LoadPostFiles in build_pass reader

the two functions which use its output don't need any of the processing
done by default_post and later prf files.

Change-Id: I160a5c2762071d5dc97ed195889196b83d8e2204
Reviewed-by: Daniel Teske <daniel.teske@theqtcompany.com>

src/plugins/qmakeprojectmanager/qmakenodes.cpp

@@ -1879,7 +1879,7 @@ EvalResult *QmakeProFileNode::evaluate(const EvalInput &input)
 
             EvalResult::EvalResultState evalResultBuildPass = EvalResult::EvalOk;
             if (ProFile *pro = readerBuildPass->parsedProFile(input.projectFilePath)) {
-                if (!readerBuildPass->accept(pro, QMakeEvaluator::LoadAll))
+                if (!readerBuildPass->accept(pro, QMakeEvaluator::LoadPreFiles))
                     evalResultBuildPass = EvalResult::EvalPartial;
                 pro->deref();
             } else {