Fix -rpath linker option for Apple build

[jackzhxng]

Summary

Fix for #12333 which broke mac runner tests on trunk, since $ORIGIN is linux only.

Test plan

ciflow/trunk

[pytorch-bot]

🔗 Helpful Links

🧪 See artifacts and rendered test results at hud.pytorch.org/pr/pytorch/executorch/13850

• 📄 Preview Python docs built from this PR

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❗ 1 Active SEVs

There are 1 currently active SEVs. If your PR is affected, please view them below:

• ROCm MI2xx CI/CD workflows failing due to : download from https://api.github.com/repos/pytorch/pytorch timed out.

❌ 1 New Failure, 2 Pending, 3 Unrelated Failures

As of commit cea5f03 with merge base 0d0769a ():

NEW FAILURE - The following job has failed:

• Build documentation / build (buck2) / Build doc (gh)
  At least one of the pre-conditions you specified did not hold

FLAKY - The following job failed but was likely due to flakiness present on trunk:

• pull / test-models-linux-basic (mv3, portable, cmake, linux.arm64.2xlarge, executorch-ubuntu-22.04-gcc11... / linux-job (gh) (matched linux rule in flaky-rules.json)
  The process '/usr/bin/git' failed with exit code 128

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

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

• pull / unittest-nxp-neutron / linux-job (gh) (trunk failure)
  test_split_group_convolution__applied_by_default
• trunk / test-huggingface-transformers-coreml (qwen3-1.7b|xnnpack|--quantize) / macos-job (gh) (trunk failure)
  RuntimeError: Command bash /Users/runner/work/_temp/exec_script failed with exit code 139

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