Removing uneeded buck deps in cmake build flow

[BujSet]

Summary

The buck and cmake build flows should be independent, where the cmake build flow should not rely on buck targets to be built or used.

Test plan

Tested on examples and tutorials, and no functional difference was seen between runs before and after change.

[pytorch-bot]

🔗 Helpful Links

🧪 See artifacts and rendered test results at hud.pytorch.org/pr/pytorch/executorch/11315

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❗ 1 Active SEVs

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❌ 1 New Failure

As of commit 992ac41 with merge base 5ef38d3 ():

NEW FAILURE - The following job has failed:

• trunk / test-llama-torchao-lowbit / macos-job (gh)
  RuntimeError: Command bash /Users/ec2-user/runner/_work/_temp/exec_script failed with exit code 134

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[BujSet]

@pytorchbot label "release notes: none"