Exclude inboxed analyzers from VerifyClosure task

[RussKie]

As per https://github.com/dotnet/designs/blob/main/accepted/2021/InboxSourceGenerators.md inboxed source generators are placed under ref/ folder, and need to be excluded from RuntimePack reference check.

Fixes broken build dotnet/windowsdesktop#1803

Tested locally manually modifying C:\Development\windowsdesktop.packages\microsoft.dotnet.sharedframework.sdk\6.0.0-beta.21363.2\targets\sharedfx.targets and getting the build to pass:

[RussKie]

Tagged as critical as we're unable to build Windows Desktop, and thus won't be able to snap for Preview7.

[ericstj]

Analyzers shouldn’t be raised as references. They are not listed as references in the framework list. This is only happening because you are making an old SDK use a new ref pack. This can go away once you pick up a Preview7 SDK with dotnet/sdk@07768a0#diff-1b35791f7e51f6b95005b2fb7aa5e65ceca0d11578158af081003c91d97b4373R80

This workaround Is fine for now, but please delete it once you update the SDK.

[ericstj]

inboxed source generators are placed under ref/ folder, and need to be excluded from RuntimePack reference check

They are not, see comment above.

[ericstj]

Ok for now but please remove after Preview7

[ryalanms]

@lukas-lansky @MattGal: Can this be merged now? Thanks.

[ryalanms]

/cc @dotnet/wpf-developers

[ericstj]

Actually, I hadn't realized this was in Arcade. You could have done this in the WindowsDesktop repo itself and save yourself having to wait for Arcade update. No need to do this in the shared framework SDK. The place to do so is here: https://github.com/dotnet/windowsdesktop/blob/2f830140b7df74ebcf518b73b9252534e751a7ef/pkg/windowsdesktop/sfx/Directory.Build.targets#L29-L40

You could simply list the single assembly name that's causing trouble: System.Text.Json.SourceGeneration

[ericstj]

Upon closer inspection, this isn't just a validation problem. Those references are actually appearing in product binaries:

C:\src\dotnet\windowsdesktop\.packages\microsoft.dotnet.sharedframework.sdk\6.0.0-beta.21363.2\targets\sharedfx.targets(467,5): error : Assembly 'DirectWriteForwarder' is missing dependency 'System.Text.Json.SourceGeneration' [C:\src\dotnet\windowsdesktop\pkg\windowsdesktop\sfx\Microsoft.WindowsDesktop.App.Runtime.sfxproj]
C:\src\dotnet\windowsdesktop\.packages\microsoft.dotnet.sharedframework.sdk\6.0.0-beta.21363.2\targets\sharedfx.targets(467,5): error : Assembly 'System.Printing' is missing dependency 'System.Text.Json.SourceGeneration' [C:\src\dotnet\windowsdesktop\pkg\windowsdesktop\sfx\Microsoft.WindowsDesktop.App.Runtime.sfxproj]

This is because C++/CLI doesn't behave like CSC WRT to only emitting references it uses. C++/CLI will produce assemblies with assembly refs regardless of whether or not the assembly is used. We need to prevent C++/CLI from seeing those references.