Adopt OSPlatformAttributes logic in aspnetcore

[JunTaoLuo]

This is a follow up to #32023. Essentially, we need to port the logic https://github.com/dotnet/runtime/blob/c7e02f3773da25946328eba150a70caa3b0e4c74/eng/versioning.targets#L53-L85 to aspnetcore.

[dougbu]

We have just two projects (Microsoft.AspNetCore.Hosting.WindowsServices and Microsoft.AspNetCore.Server.Kestrel.Transport.Quic) where any [assembly: SupportedOSPlatform(...)] instances were deemed necessary. It's not clear where what we have is insufficient.

Why do we need anything different from the current infrastructure❔ In particular, why do we need either additional [assembly: SupportedOSPlatform(...)] attributes or the complicated logic from the dotnet/runtime repo❔

[dougbu]

/btw https://github.com/dotnet/runtime/blob/main/eng/versioning.targets#L73 looks like a significant bug @jeffhandley

[jeffhandley]

/btw https://github.com/dotnet/runtime/blob/main/eng/versioning.targets#L73 looks like a significant bug @jeffhandley

That code is right, but it highlights just how badly named the <SupportedPlatform> property is. 😟 <SupportedPlatform> is actually used to specify which platforms the analyzer is expected to check for compatibility--not which platforms are actually supported. There is no MSBuild property for which platforms are actually supported--that's done through the OSPlatform attributes. In the runtime repo though, we populate the OSPlatform attributes using MSBuild properties of <SupportedOSPlatform> and <UnsupportedOSPlatform>. Sooooo similar in name.

The code you linked to is ensuring that for every <SupportedOSPlatform> and every <UnsupportedOSPlatform> that the assembly is configured for, we include the platform in the <SupportedPlatform> MSBuild property to make sure the analyzer checks compatibility for the platform. The CA1418 analyzer will produce warnings for any platforms used in attributes that aren't included in the <SupportedPlatform> list.

Thanks for the tag on this regardless. It really emphasizes the poor naming.
/cc @terrajobst

[dougbu]

Discussed offline and @JunTaoLuo has decided not to be passionate. Closing since duplicating what dotnet/runtime has wouldn't simplify our infrastructure.