Fix library substitution again which broke when I merged all the
library related pieces of information.
Keep Qt and 3rdparty libraries separate so that dbus does not get
mapped into Qt::DBus (or the other way around).
Make names in helper.py more consistent while at it.
Change-Id: I5e5bf02bdabf8bafe991c5701deca76bde4df2c3
Reviewed-by: Alexandru Croitor <alexandru.croitor@qt.io>