qtserialport-examples.html not always correctly generated

While packaging qtserialport 5.4 in Ubuntu, I have noticed that doc/qtserialport/qtserialport-examples.html is not always generated.

When building the source for the first time, a file named examples-serialport.html is generated instead, and that file has incomplete contents (i.e. the list of examples is empty). When building for the second time, everything goes correctly and qtserialport-examples.html is generated (and examples-serialport.html is not.

I am attaching both files so that you can see the difference between them.

This problem can also be visible online: http://doc.qt.io/qt-5/examples-serialport.html (there is no actual list of examples there).

Note: I am not saying that this problem affects only qtserialport, most probably it affects other modules as well.