[Reland] Skip building Apple demo app on fork PRs

[huydhn]

Relanding #6865 as it has been reverted by #6868 probably due to a land race.

As pointed out by @swolchok in #6538 (comment), I also include test-huggingface-transformers here as it looks simple enough. Different cases, same root cause about missing secrets on forks.

[pytorch-bot]

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✅ You can merge normally! (1 Unrelated Failure)

As of commit f0466e0 with merge base a64ed1b ():

BROKEN TRUNK - The following job failed but were present on the merge base:

👉 Rebase onto the `viable/strict` branch to avoid these failures

• trunk / test-coreml-delegate / macos-job (gh) (trunk failure)
  RuntimeError: Command bash /Users/runner/work/_temp/exec_script failed with exit code 1

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