Normally you ask them for the object files, but those specific guys are middleware developers so they provide QtCreator configured to build with their library (to get a different Qt version, select a different Qt Kit in QtCreator settings).
Additionally, the nature of the library is that it's probably a plugin that's loaded by a regular Qt application, as a result you've got their classes available in the QML scripts. It isn't very intrusive on the practical level.
you ask them for the LGPL package, they send it to you, you compile ?
The onus is on the person making the app that links against the LGPL library to provide you with the build instruction.
At worse they would give you their main static library and Qt LGPL source code and you just have to relink them and open Xcode to upload it to your iDevice ?
I am not talking primarily about open source projects, but about closed source projects with LGPL components on app stores. You’d need the proprietary main object from them. Also, requiring that your users have an Apple dev account before they can execute their rights is problematic at best. I am not alone in rejecting Qt on these grounds, in favour of some MIT or similarly licensed alternative.
Static/dynamic linking isn't a problem.