Clang: Use timer in ClangIpcServer in the file watcher to send diagnostics

One mechanism for all diagnostic updates is better to maintain.

Change-Id: I774577bfa343162ded362977a0727a12379d1eab
Reviewed-by: Nikolai Kosjar <nikolai.kosjar@theqtcompany.com>

src/tools/clangbackend/ipcsource/clangipcserver.cpp

@@ -69,6 +69,10 @@ ClangIpcServer::ClangIpcServer()
     QObject::connect(&sendDiagnosticsTimer,
                      &QTimer::timeout,
                      [this] () { translationUnits.sendChangedDiagnostics(); });
+
+    QObject::connect(translationUnits.clangFileSystemWatcher(),
+                     &ClangFileSystemWatcher::fileChanged,
+                     [this] () { sendDiagnosticsTimer.start(); });
 }
 
 void ClangIpcServer::end()