AutoTest: Fix handling of cpp files for Quick tests

Modifying C++ files of Quick tests had been ignored as they
normally have little impact.
But nevertheless this behavior is wrong and could lead to
unexpected behavior later on if no complete rescan had been
done and even with a rescan there could have been some
cached artifacts.
Fix this by tracking the paths of the C++ files that hold
the main() or the respective macro to be able to handle
changes of these files correctly as well.

Task-number: QTCREATORBUG-20746
Change-Id: Iec860aa63ffd167511efdbf63a6ffa369f094edf
Reviewed-by: David Schulz <david.schulz@qt.io>

src/plugins/autotest/quick/quicktestparser.h

@@ -51,11 +51,12 @@ public:
     void release() override;
     bool processDocument(QFutureInterface<TestParseResultPtr> futureInterface,
                          const QString &fileName) override;
+    QString projectFileForMainCppFile(const QString &fileName) const;
 signals:
     void updateWatchPaths(const QStringList &directories) const;
 private:
     bool handleQtQuickTest(QFutureInterface<TestParseResultPtr> futureInterface,
-                           CPlusPlus::Document::Ptr document, const Core::Id &id) const;
+                           CPlusPlus::Document::Ptr document, const Core::Id &id);
     void handleDirectoryChanged(const QString &directory);
     void doUpdateWatchPaths(const QStringList &directories);
     QList<QmlJS::Document::Ptr> scanDirectoryForQuickTestQmlFiles(const QString &srcDir) const;
@@ -63,6 +64,7 @@ private:
     QHash<QString, QString> m_proFilesForQmlFiles;
     QFileSystemWatcher m_directoryWatcher;
     QMap<QString, QMap<QString, QDateTime> > m_watchedFiles;
+    QMap<QString, QString> m_mainCppFiles;
 };
 
 } // namespace Internal