don't set m_sourceRoot if it equals m_buildRoot

Change-Id: I3e20c2a9b4455f7e9fcc60202166d1a8a079cba2
Reviewed-by: Daniel Teske <daniel.teske@nokia.com>
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@nokia.com>

src/shared/proparser/qmakeevaluator.cpp

@@ -986,7 +986,8 @@ bool QMakeEvaluator::prepareProject(const QString &inDir)
                 if (!IoUtils::exists(cachefile))
                     cachefile.clear();
                 if (!conffile.isEmpty() || !cachefile.isEmpty()) {
-                    m_sourceRoot = sdir;
+                    if (dir != sdir)
+                        m_sourceRoot = sdir;
                     m_buildRoot = dir;
                     break;
                 }