build works, runs fine, merging!

Released in 0dbd1b8 to address #31045 and #31047.

I thought that this is another example why we need to integrate content addressed upstream sources (my current work involving IPFS and Nix is part of this). But then I realised skype is a proprietary software. If there are restrictions to redistribution, does that mean it's not allowed to have skype source/binaries in IPFS and for Nixpkgs to use that as the upstream source?

That's so:

This license does not give you any right to, and you may not:
iv. publish, copy, rent, lease, sell, export, import, distribute, or lend the software or the Services, unless Microsoft expressly authorizes you to do so;

https://www.microsoft.com/en-us/servicesagreement/?intsrc=client-_-linux-_-1427%2F5.5.0.1%2F-_-menu.tou&setlang=en

Nixpkgs distinguish between unfree and unfreeRedistributable licenses, you can use that to cache the latter.