This issue is now fixed by commit rev#103470.
It was related to WEL (not specific to EiffelBuild).
See https://svn.eiffel.com/websvn/comp.php?repname=eiffelstudio&compare[]=%2F@103469&compare[]=%2F@103470

The correction will be available in next release (19.11 or beta version 19.09).