qvkgen shows warnings after header.LGPL is removed

"Failed to open header.LGPL"

After https://codereview.qt-project.org/c/qt/qtbase/+/315716 the attempt to paste the license header from header.LGPL fails. The cpp and h files are still generated, so it is not fatal. Something needs to be figured out to avoid attempting to read non-existing files. (do we need the license header in the generated files in the first place?)