Update dependencies from https://github.com/dotnet/arcade build 20200129.8 (#6261)

- Microsoft.DotNet.Arcade.Sdk - 5.0.0-beta.20079.8

eng/common/tools.ps1

@@ -655,6 +655,9 @@ Write-PipelineSetVariable -Name 'Artifacts.Log' -Value $LogDir
 Write-PipelineSetVariable -Name 'TEMP' -Value $TempDir
 Write-PipelineSetVariable -Name 'TMP' -Value $TempDir
 
+$env:TEMP=$TempDir
+$env:TMP=$TempDir
+
 # Import custom tools configuration, if present in the repo.
 # Note: Import in global scope so that the script set top-level variables without qualification.
 if (!$disableConfigureToolsetImport) {