Fix "dotnet build Kestrel.slnf"

[halter73]

Build error before fix:

F:\dev\dotnet\aspnetcore\src\Servers\Kestrel [master ≡]> dotnet build .\Kestrel.slnf
Microsoft (R) Build Engine version 16.9.0-preview-20513-07+c10f34c4e for .NET
Copyright (C) Microsoft Corporation. All rights reserved.

F:\dev\dotnet\aspnetcore\AspNetCore.sln(7882): Solution file error MSB5023: Error parsing the nested project section in solution file. A project with the GUID "{884AED21-7931-42A3-B08A-E58F7B0D6E7F}" is listed as being nested under project "{017429CC-C5FB-48B4-9C46-034E29EE2F06}", but does not exist in the solution.

Build FAILED.

I wonder if there's a good way to prevent this from regressing. The slnf's appear to be especially susceptible to breaking compared to the old sln's. I just fixed this a few months ago. Maybe we could just add a test that calls dotnet build Kestrel.slnf and verifies a successful status code.

[HaoK]

I think we used to have azdo pipeline that would just run build on all the various subfolders, at least I recall seeing that last year at some point, I think @mkArtakMSFT might have some more details, but seems like useful if we could setup to run once a day just to ensure its green?

[danirzv]

I'm facing same error and i cant figure out why

[ghost]

Hi @danirzv. It looks like you just commented on a closed PR. The team will most probably miss it. If you'd like to bring something important up to their attention, consider filing a new issue and add enough details to build context.