build: Few build adjustments to reduce flakiness (backport #700)

[mergify]

This is an automatic backport of pull request #700 done by Mergify.
Cherry-pick of f622a0d has failed:

On branch mergify/bp/legacy/3x/pr-700
Your branch is up to date with 'origin/legacy/3x'.

You are currently cherry-picking commit f622a0d.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Changes to be committed:
	modified:   build/workflow/stage-build-packages.yml
	modified:   src/Directory.Packages.props
	modified:   src/library/Uno.Toolkit.Cupertino/Uno.Toolkit.WinUI.Cupertino.csproj

Unmerged paths:
  (use "git add/rm <file>..." as appropriate to mark resolution)
	both modified:   samples/Directory.Packages.props
	deleted by us:   samples/Uno.Toolkit.Samples/Directory.Build.targets
	both modified:   src/Directory.Build.targets

To fix up this pull request, you can check it out locally. See documentation: https://docs.github.com/en/github/collaborating-with-pull-requests/reviewing-changes-in-pull-requests/checking-out-pull-requests-locally

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