Per-OS prereq knowledge

[rainersigwald]

I tried dotnetup on a fresh Ubuntu 26.04 WSL instance, and it failed because I didn't have ICU installed. I recognized that pretty quickly but had to click around a bit to get to https://learn.microsoft.com/dotnet/core/install/linux-ubuntu-install?tabs=dotnet10&pivots=os-linux-ubuntu-2604#dependencies to figure out that I needed libicu78.

It'd be great if dotnetup could emit a "please install .NET's prereqs, here is a command line to paste" message in a failure case like this.

[dsplaisted]

This has now been fixed with #54802 (by dropping the ICU requirement for Linux).

[dsplaisted]

So now dotnetup will run and install an SDK without ICU, but when you try to actually use the SDK it will probably still fail. We have an issue tracking how to handle detecting / installing native dependencies for .NET: #51113