AUTOUIC: Fix cyclic dependency between generated UI headers and timestamp
Once the generated UI headers are created by UIC they also are
involved into processing in next run on ninja. Autogen adds
files to the deps file
ui_*.h and this cause timestamp start depend on
ui_*.h depend on timestamp because of the explicit
rules added by !5803 (merged).
This avoids adding the
ui_*.h to deps file at second ninja run.