CMakePM: Scan files only on CMake configuration failure

The file tree scanner will only be started on CMake configuration
failure to generate the <File System> fall back project node.

Change-Id: I873ef1189fd43dc9bffa03aeafabb00bb3b8b6af
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: Eike Ziller <eike.ziller@qt.io>

src/plugins/cmakeprojectmanager/fileapidataextractor.h

@@ -75,10 +75,6 @@ public:
 FileApiQtcData extractData(FileApiData &data,
                            const Utils::FilePath &sourceDirectory,
                            const Utils::FilePath &buildDirectory);
-FileApiQtcData generateFallbackData(const Utils::FilePath &topCmakeFile,
-                                    const Utils::FilePath &sourceDirectory,
-                                    const Utils::FilePath &buildDirectory,
-                                    QString errorMessage);
 
 } // namespace Internal
 } // namespace CMakeProjectManager