If we have encountered a "FATAL ERROR" we can afford writing a line to stderr

There is no guarantee that if something is wrong, the
Application::ShowNativeErrorBox() will manage to show anything, is
there? And this code might be invoked in a program that doesn't even
have any GUI. So at least try to show the message on stderr, too.

Change-Id: Ieb11a6f490c26c773af646ed7e9c3cf6ccb4a669
Reviewed-on: https://gerrit.libreoffice.org/62550Reviewed-by: Michael Meeks <michael.meeks@collabora.com>
Tested-by: Michael Meeks <michael.meeks@collabora.com>

desktop/source/app/app.cxx

@@ -376,6 +376,7 @@ void FatalError(const OUString& sMessage)
 
     OUString sTitle = sProductKey + " - Fatal Error";
     Application::ShowNativeErrorBox (sTitle, sMessage);
+    std::cerr << sTitle << ": " << sMessage << std::endl;
     _exit(EXITHELPER_FATAL_ERROR);
 }