CMake: Fix pipe name on windows

Fix the name of the pipe used to talk to cmake-server on windows. The name needs
to follow a very specific pattern there.

Change-Id: I2789be43b374d008e2bf784563ab362efd891e59
Reviewed-by: Tobias Hunger <tobias.hunger@qt.io>

src/plugins/cmakeprojectmanager/servermode.h

@@ -104,6 +104,7 @@ private:
     const QString m_extraGenerator;
     const QString m_platform;
     const QString m_toolset;
+    QString m_socketName;
     const bool m_useExperimental;
     bool m_gotHello = false;
     bool m_isConnected = false;