Allow Copilot to access vsassets.io urls to enable restore

[baronfel]

In #49459 Copilot couldn't compile to check its code because it couldn't access some urls.

We can setup copilot steps by making a special actions workflow, and in that workflow we can define env vars that include an allowlist.

Docs: https://docs.github.com/en/copilot/customizing-copilot/customizing-the-development-environment-for-copilot-coding-agent
Variable to set: COPILOT_AGENT_FIREWALL_ALLOW_LIST_ADDITIONS
Domain to allow: vsblob.vsassets.io

Warning

Firewall rules blocked me from connecting to one or more addresses

I tried to connect to the following addresses, but was blocked by firewall rules:

• 7tjvsblobprodcus341.vsblob.vsassets.io
  • Triggering command: dotnet build src/Tasks/Microsoft.NET.Build.Tasks/Microsoft.NET.Build.Tasks.csproj --verbosity minimal --no-restore (dns block)
• c78vsblobprodcus322.vsblob.vsassets.io
  • Triggering command: dotnet build src/Tasks/Microsoft.NET.Build.Tasks/Microsoft.NET.Build.Tasks.csproj --verbosity minimal --no-restore (dns block)
• d0svsblobprodcus381.vsblob.vsassets.io
  • Triggering command: dotnet build src/Tasks/Microsoft.NET.Build.Tasks/Microsoft.NET.Build.Tasks.csproj --verbosity minimal --no-restore (dns block)
• jd4vsblobprodcus366.vsblob.vsassets.io
  • Triggering command: dotnet build src/Tasks/Microsoft.NET.Build.Tasks/Microsoft.NET.Build.Tasks.csproj --verbosity minimal --no-restore (dns block)
• l49vsblobprodcus358.vsblob.vsassets.io
  • Triggering command: dotnet build src/Tasks/Microsoft.NET.Build.Tasks/Microsoft.NET.Build.Tasks.csproj --verbosity minimal --no-restore (dns block)
• lylvsblobprodcus31.vsblob.vsassets.io
  • Triggering command: dotnet build src/Tasks/Microsoft.NET.Build.Tasks/Microsoft.NET.Build.Tasks.csproj --verbosity minimal --no-restore (dns block)
• uy6vsblobprodcus34.vsblob.vsassets.io
  • Triggering command: dotnet build src/Tasks/Microsoft.NET.Build.Tasks/Microsoft.NET.Build.Tasks.csproj --verbosity minimal --no-restore (dns block)
• vb4vsblobprodcus33.vsblob.vsassets.io
  • Triggering command: dotnet build src/Tasks/Microsoft.NET.Build.Tasks/Microsoft.NET.Build.Tasks.csproj --verbosity minimal --no-restore (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to my firewall allow list

Originally posted by @Copilot in #49459 (comment)