[larma]

He is talking about the possibility to build AOSP without certain propriatry (native) libraries that are used to communicate with the device components. While you always need them at runtime for a lot of features (but some devices run in wifi-only mode without prorietary libs) it was possible to build without them because of the way they're linked. This was changed in Nougat where it became impossible to build the source code for certain Nexus devices, because during build process there are references to the source code of some proprietary libraries. I had this problem myself while building AOSP for Nexus 5X and can confirm it.