Clang: Collect source dependencies

It is quite easy because we track the include directives in the
preprocessor callbacks.

Change-Id: I2d7bd67b31f50c0d8d4a46c57e83dffa0c558dc7
Reviewed-by: Ivan Donchevskii <ivan.donchevskii@qt.io>

src/tools/clangrefactoringbackend/source/collectmacrossourcefilecallbacks.cpp

@@ -39,6 +39,7 @@ bool CollectMacrosSourceFileCallbacks::handleBeginSource(clang::CompilerInstance
                 m_sourceFiles,
                 m_usedMacros,
                 m_fileInformations,
+                m_sourceDependencies,
                 m_filePathCache,
                 compilerInstance.getSourceManager(),
                 compilerInstance.getPreprocessorPtr());