Communicate build script breaking change around branding option

[MichaelSimons]

The breaking change made with dotnet/dotnet#3574 and dotnet/dotnet#3668 needs an announcement posted. Should post a notice of it coming prior to the release and then link to it in the release announcement.

[ViktorHofer]

The breaking change is part of 10.0.102.

[mthalman]

Announcement posted: #5435

[ViktorHofer]

Thanks a lot @mthalman