MSBUILD Server dogfood

[SimaTian]

MSBUILD Server dogfood

Part of #9379

Please help us with our dofgooding effort for the MSBuild server feature.
For now we've dogfooded internally for our pipelines, we're running without issues within Aspnetcore and we would like to continue the rollout before we're confident enough to make Server build the new default.

[Copilot]

Pull Request Overview

This PR enables the MSBuild server feature in CI by setting the MSBUILDUSESERVER variable.

• Introduces a new pipeline variable to dogfood the MSBuild server
• Enables internal rollout for AspNetCore builds

Comments suppressed due to low confidence (1)

eng/pipelines/common/variables.yml:47

• [nitpick] The variable name is in all-caps without separators; consider using a consistent naming style (e.g., camelCase or kebab-case) to match other pipeline variables.

name: MSBUILDUSESERVER

[SimaTian]

Note: I'm not familiar with your pipelines. Turning on MSBUILD server is done via setting the environment variable MSBUILSUSESERVER to 1 so that is what I was trying to achieve.
If there is a better place to do it, please let me know.

While checking the binlog of the failed check it claims that MSBUILDUSESERVER=0 so I probably placed the variable at a wrong spot.
Or maybe I have to set env:MSBUILDUSESERVER=1 instead?
Any insight will be appreciated.