Link backend to prtable libs

[neuropilot-captain]

Summary

1. Link portable OPs and kernels
2. Remove unused cmake checks

[pytorch-bot]

🔗 Helpful Links

🧪 See artifacts and rendered test results at hud.pytorch.org/pr/pytorch/executorch/12268

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✅ You can merge normally! (2 Unrelated Failures)

As of commit 9c0279d with merge base ba19c75 ():

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

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

• pull / test-models-linux (mobilebert, portable, linux.2xlarge) / linux-job (gh) (trunk failure)
  ##[error]The operation was canceled.
• pull / test-models-linux (mobilebert, xnnpack-quantization-delegation, linux.2xlarge) / linux-job (gh) (trunk failure)
  ##[error]The operation was canceled.

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[cccclai]

Ah does it mean the previous models are fully lowered?