FreeBSD official build leg fails

[dagood]

Build: https://dev.azure.com/dnceng/internal/_build/results?buildId=69569

/mnt/resource/agent/_work/3/s/src/pkg/projects/Microsoft.NETCore.App/Microsoft.NETCore.App.pkgproj(62,5):
  error MSB4062: The "GenerateFileVersionProps" task could not be loaded from the assembly /mnt/resource/agent/_work/3/s/Tools/local/netstandard2.0/core-setup.tasks.dll.
  Assembly with same name is already loaded Confirm that the <UsingTask> declaration is correct, that the assembly and all its dependencies are available, and that the task contains a public class that implements Microsoft.Build.Framework.ITask.

This issue tracks fixing this and reenabling this leg.

[dagood]

In source-build, I've experienced this sort of error when MSBuild node reuse is enabled. The --ci/-ci Arcade script option disables node reuse, and our builds aren't currently passing it--adding it is probably the fix.

[dagood]

Forgot that even though we have Arcade scripts in the repo, we don't use them yet. /nr:false is the MSBuild arg way, and MSBUILDDISABLENODEREUSE=1 is an env var way.

[dagood]

Fixed, successful internal build: https://dev.azure.com/dnceng/internal/_build/results?buildId=70295&_a=summary

[dagood]

This kind of issue happened again when Core-Setup built within 10 minutes of CoreCLR building, although Microsoft.Build.Tasks.CodeAnalysis.dll failed this time (for task Microsoft.CodeAnalysis.BuildTasks.Csc): https://dev.azure.com/dnceng/internal/_build/results?buildId=77984.

I noticed that Core-Setup has some Exec tasks that run dotnet msbuild commands, so I think we need to use the env var approach to make sure the setting propagates into that inner command. Submitting a PR to add that.

[dagood]

FreeBSD agents are now not accepting jobs. Internal mail thread ongoing: seems to be that there's a new agent version needed.

[dagood]

Removed leg temporarily with dotnet/core-setup#5035 to unblock the build.

[dagood]

The infra issue should be over, so the leg should work if we enabled it. Filed https://github.com/dotnet/core-setup/issues/5083 to track that.

(Note: the leg is still disabled right now.)