LabVIEW currently does not support this feature in it's Application Builder. One way to get around this is by building your complete LabVIEW installer, and then wrapping that installer from within a third-party installation creator that supports Product Key Registration.
Also, are you aware of the LabVIEW Idea Exchange? It's a place where you can create an Idea for a feature request that NI will consider implementing in future versions of LabVIEW. Ideas that receive a lot of Kudos will probably be more likely to be implemented. Here is a link to an Idea that requests the feature you want, so I would suggest you give Kudos to that Idea.
