Change netcoreapp5.0 to net5.0

[ViktorHofer]

No Merge. Part of batched rollout in May: #35202

Contributes towards dotnet/sdk#10756
Requires dotnet/arcade#5292

I will create a doc after merging this which describes when to use which condition. Basically the recommendation is:

1. Use an equality check if the TargetFramework isn't overloaded with the OS portion.
2. Use a StartsWith when you want to test for .NETStandard or .NETFramework
3. Use a StartsWith if the TargetFramework is overloaded with the OS portion.
4. Use negations if that makes the conditions easier.

cc @ericstj

[ghost]

Tagging subscribers to this area: @ViktorHofer
Notify danmosemsft if you want to be subscribed.

[Anipik]

We will need to change our custom parsing for the designTimeBuilds as well.

[ViktorHofer]

We will need to change our custom parsing for the designTimeBuilds as well.

Master already has the net5.0 parsing logic: https://github.com/dotnet/runtime/blob/master/src/libraries/intellisense.targets#L42-L54, dotnet/sdk@0f5fc4b

[safern]

Should this instead test for equality?

[ViktorHofer]

No, because the TargetFramework is overloaded with the OS: netcoreapp5.0-Windows_NT.
I will create a doc after merging this which describes when to use what. Basically the recommendation is:

1. Use an equality check if the TargetFramework isn't overloaded with the OS portion.
2. Use a StartsWith when you want to test for multiple .NETStandard or .NETFramework versions
3. Use a StartsWith if the TargetFramework is overloaded with the OS portion.
4. Use negations if that makes the conditions easier.

[ahsonkhan]

What about netcoreapp3.1?

[safern]

We don’t build System.Text.Json for netcoreapp3.1 and we shouldn’t need as it has been inbox since netcoreapp3.0.

Also it seems like we shouldn’t need to cross build System.Text.Json for netcoreapp3.0 since it is inbox and the package should just contain an inbox placeholder:

https://github.com/dotnet/runtime/blob/master/src/libraries/pkg/baseline/packageIndex.json#L6253

[ViktorHofer]

We should do a pass over all our OOBs at some point and make sure that we only build what's actually necessary. This will help us keep our build configuration and conditions sane.

[ghost]

Hello @ViktorHofer!

Because this pull request has the auto-merge label, I will be glad to assist with helping to merge this pull request once all check-in policies pass.

p.s. you can customize the way I help with merging this pull request, such as holding this pull request until a specific person approves. Simply @mention me (@msftbot) and give me an instruction to get started! Learn more here.