[OE-core] Passing additional data from packages to be used during image creation

[Pascal Bach]

I would like to pass some additional data generated during the creation of a package to the image creation step.
The idea is to use this data to generate a more detailed manifest of what is included in the image. In the concrete case
I would like to pass a list of required copyright files that need to be checked for during image creation.

My current approach is to add this list as a new variable COPYRIGHTS to the pkgdata of each package.
Using the image manifest to determine the package this allows me to compile a list of all required copyrights.

The following patch allows to add extra variables to pkgdata and thus allows to pass additional data

- [PATCH] package.bbclass: allow additional variables to be added to

Is this a valid approach or did a miss a simpler way to access any package data during image creation?

Pascal