Clean vcpkg artifacts on solution clean

[Trenly]

📖 Description

Add a CleanVcpkg target in src\vcpkg.props so Visual Studio Clean Solution removes repository-local vcpkg artifacts.

The target:

• Deletes $(VcpkgInstalledDir) (src\vcpkg_installed\)
• Deletes src\VcpkgPortOverlay\.created so overlay ports regenerate on next build

Also adds an XML comment block explaining why this cleanup is necessary.

🔗 References

Resolves #6338

🔍 Validation

Manual local verification of MSBuild target wiring only.

✅ Checklist

• Signed the Contributor License Agreement
• Linked to an issue
• Updated Release Notes (if applicable)
• Updated documentation (if applicable)
• Updated Copilot instructions (if build, architecture, or conventions changed)

📋 Issue Type

• Bug fix
• Feature
• Task

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Assisted-by: GitHub Copilot

Microsoft Reviewers: Open in CodeFlow

[florelis]

/azp run

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[florelis]

What's the scenario you're thinking about that may require cleaning the vcpkgs?
I can only think of the case where you are updating the ports from our custom overlay. If that is the only case, maybe we don't need it in most cases and could have it gated behind some option, or make the target smarter to only clean up when the ports changed.

[Trenly]

What's the scenario you're thinking about that may require cleaning the vcpkgs? I can only think of the case where you are updating the ports from our custom overlay. If that is the only case, maybe we don't need it in most cases and could have it gated behind some option, or make the target smarter to only clean up when the ports changed.

Take for example #6301 - That was only discovered because I removed the vcpkgs. In most workflows, I would expect "Clean" to remove all build artifacts and produce a 100% brand new build - which wasn’t the case.

While a simple rebuild would skip updating the vcpkgs, if I am explicitly running a clean, I would have thought that the vcpkgs would have also been cleaned up too - regardless of if there were port changes or not. In my mind, Clean means to perform the next build as if it were the first build the system ever ran