qga: Fix a memory leak

The string returned by g_win32_error_message() has to be
deallocated with g_free().

Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Message-Id: <20200228100726.8414-5-philmd@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>

qga/channel-win32.c

@@ -302,8 +302,8 @@ static gboolean ga_channel_open(GAChannel *c, GAChannelMethod method,
                            OPEN_EXISTING,
                            FILE_FLAG_NO_BUFFERING | FILE_FLAG_OVERLAPPED, NULL);
     if (c->handle == INVALID_HANDLE_VALUE) {
-        g_critical("error opening path %s: %s", newpath,
-                   g_win32_error_message(GetLastError()));
+        g_autofree gchar *emsg = g_win32_error_message(GetLastError());
+        g_critical("error opening path %s: %s", newpath, emsg);
         return false;
     }