Nightly build: don't push vpack

[kmahone]

I am setting up a scheduled Pipeline build to run the equivalent of what we run for the Release build. This is so that if there are any issues with this Pipeline we will catch it early rather than just at the time where we are running a release.

One thing we don't want to do in this nightly build is to push the various vpacks. This is for two reasons:

1. The versions would collide with the Release Pipeline, since we don't do anything to differentiate them.
2. We would be pushing a bunch of vpacks that we don't intend to use

So, we set a condition on the 'vpack push' tasks to only push in the 'real' release pipeline.

This fix is related to #6174.

[kmahone]

/azp run

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[StephenLPeters]

There is a corresponding change the the pipelines to use this new variable as well I assume.

[kmahone]

There is a corresponding change the the pipelines to use this new variable as well I assume.

Yes. The variable is set to true on the 'real' ReleaseBuild Pipeline and 'false' on the 'test' Pipeline.

[ghost]

🎉Microsoft.UI.Xaml v2.8.0-prerelease.220712001 has been released which incorporates this pull request.:tada:

Handy links:

• Release Notes
• Official Nuget Release

[ghost]

🎉Microsoft.UI.Xaml v2.8.0 has been released which incorporates this pull request.:tada:

Handy links:

• Release Notes
• Official Nuget Release