arcade: Arcade flow into arcade-validation is failing PR validation

• This issue is blocking This blocks arcade promotion
• This issue is causing unreasonable pain

Dependency update PR https://github.com/dotnet/arcade-validation/pull/2360 is failing its helix validation leg with the following errors:

+ dotnet exec --roll-forward Major --runtimeconfig Validation.Tests.runtimeconfig.json --depsfile Validation.Tests.deps.json /home/helixbot/work/BE770A59/p/xunit-runner/tools/netcoreapp2.0/xunit.console.dll Validation.Tests.dll -nocolor -xml testResults.xml
It was not possible to find any compatible framework version
The framework 'Microsoft.NETCore.App', version '6.0.0-preview.4.21253.7' was not found.
  - The following frameworks were found:
      6.0.0-preview.3.21201.4 at [/home/helixbot/work/BE770A59/p/dotnet-cli/shared/Microsoft.NETCore.App]

You can resolve the problem by installing the specified framework and/or SDK.

The specified framework can be found at:
  - https://aka.ms/dotnet-core-applaunch?framework=Microsoft.NETCore.App&framework_version=6.0.0-preview.4.21253.7&arch=x64&rid=debian.9-x64
+ export _commandExitCode=150

This is more than likely caused by the upgrade to the preview 4 sdk: https://github.com/dotnet/arcade/commit/130a085011ed5d5ef0fd30e07fa16ce88c2df28a