Work around QLocalSocket::error deprecation

Centralizing does not bring much benefit here, it's just six locations,
and having either a central #include <QLocalSocket> in algorithm.h
or a separe file does not sound better.

In any case, it is absurd, that deprecating functions to "make code
nicer" requires spilling #if QT_VERSION_CHECK over the code.

Change-Id: Ia9a8c0eb6ef7cabbaffb46cfe472247e26e7e2c2
Reviewed-by: Eike Ziller <eike.ziller@qt.io>

src/libs/clangsupport/connectionclient.cpp

@@ -324,8 +324,15 @@ void ConnectionClient::connectStandardOutputAndError(QProcess *process) const
 
 void ConnectionClient::connectLocalSocketError() const
 {
+    constexpr void (QLocalSocket::*LocalSocketErrorFunction)(QLocalSocket::LocalSocketError)
+#if QT_VERSION < QT_VERSION_CHECK(5, 15, 0)
+            = &QLocalSocket::error;
+#else
+            = &QLocalSocket::errorOccurred;
+#endif
+
     connect(m_localSocket,
-            QOverload<QLocalSocket::LocalSocketError>::of(&QLocalSocket::error),
+            LocalSocketErrorFunction,
             this,
             &ConnectionClient::printLocalSocketError);
 }