Ship the OpenVINO delegate as its own library

[shoumikhin]

The OpenVINO delegate was compiled into the Python extension, so only Python could
use it. A C++ application had no way to link it from the wheel, which is the same gap
the other delegates had before they were split out.

It now builds as its own library and ships beside the runtime, so an application can
ask for it:

find_package(executorch REQUIRED COMPONENTS backend_openvino)
target_link_libraries(my_app PRIVATE executorch::backend_openvino)

Only the adapter ships here. The OpenVINO runtime itself is loaded at run time and is
not part of the wheel, so the component's documentation says to install it separately,
and the wheel does not grow meaningfully: the adapter is a few kilobytes.

The library resolves the runtime from the shared runtime library rather than from the
static core, so the delegate registers into the one registry the process has instead of
a second private one.

Test Plan: built a wheel with OpenVINO enabled on Linux x86_64 and inspected it.
The library ships at executorch/lib/libexecutorch_backend_openvino.so. Its delegate
symbols moved out of the Python extension, 13 in the library and 0 in the extension,
so the process has one copy and one registration. Its only ExecuTorch dependency is
the shared runtime library, and it records no link dependency on OpenVINO, confirming
the runtime is still loaded at run time. Added an ownership row to the shared library
test so a future change that puts the delegate back into the extension fails there.

cc @digantdesai @freddan80 @per @zingo @oscarandersson8218 @mansnils @Sebastian-Larsson @robell @rascani

[shoumikhin]

Stack from ghstack (oldest at bottom):

• Name the Python extension after what it contains #21816
• Ship linkable libraries in the macOS wheel #21771
• -> Ship the OpenVINO delegate as its own library #21770
• Build and publish CUDA wheels #21668
• Ship the CUDA delegate in the wheel #21645
• Ship the quantized kernels as their own library #21642
• Ship a C++ SDK in the wheel #21639
• Split the runtime out of the Python bindings extension #21610

[pytorch-bot]

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🧪 See artifacts and rendered test results at hud.pytorch.org/pr/pytorch/executorch/21770

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❌ 4 New Failures, 1 Unrelated Failure, 8 Unclassified Failures

As of commit 765de9e with merge base ed2d9ec ():

NEW FAILURES - The following jobs have failed:

• pull / test-quantized-aot-lib-linux / linux-job (gh)
  ##[error]fatal: unable to access 'https://github.com/zeux/volk/': Error in the HTTP2 framing layer
• Test CUDA Builds / export-model-cuda-artifact (SocialLocalMobile, Qwen3.5-35B-A3B-HQQ-INT4, quantized-int4-tile-packed) / linux-job (gh)
  RuntimeError: Command bash /__w/_temp/exec_script failed with exit code 1
• Test CUDA Windows Export and E2E / export-model-cuda-windows-artifact (nvidia, parakeet-tdt, quantized-int4-weight-only) / linux-job (gh)
  RuntimeError: Command docker exec -t 7084ec80e884901c95beed4a7bc771104f132b0573ec395846ad515117e5d892 /exec failed with exit code 1
• trunk / test-models-macos-cpu (efficient_sam, portable) / macos-job (gh)
  RuntimeError: Command bash /Users/ec2-user/runner/_work/_temp/exec_script failed with exit code 1

UNCLASSIFIED FAILURES - DrCI could not classify the following jobs because the workflow did not run on the merge base. The failures may be pre-existing on trunk or introduced by this PR:

• Build Linux CUDA Wheels / pytorch/executorch / build-manywheel-py3_10-cuda12_6 (gh) (this job did not run on the merge base, so DrCI cannot tell whether the failure is pre-existing)
  AssertionError: no CUDA device is visible to this x86_64 row, which is the row that proves the delegate computes. The runner lost its GPU or the installed torch cannot reach it; either way nothing here executed.
• Build Linux CUDA Wheels / pytorch/executorch / build-manywheel-py3_10-cuda13_0 (gh) (this job did not run on the merge base, so DrCI cannot tell whether the failure is pre-existing)
  AssertionError: no CUDA device is visible to this x86_64 row, which is the row that proves the delegate computes. The runner lost its GPU or the installed torch cannot reach it; either way nothing here executed.
• Build Linux CUDA Wheels / pytorch/executorch / build-manywheel-py3_12-cuda12_6 (gh) (this job did not run on the merge base, so DrCI cannot tell whether the failure is pre-existing)
  AssertionError: no CUDA device is visible to this x86_64 row, which is the row that proves the delegate computes. The runner lost its GPU or the installed torch cannot reach it; either way nothing here executed.
• Build Linux CUDA Wheels / pytorch/executorch / build-manywheel-py3_12-cuda13_2 (gh) (this job did not run on the merge base, so DrCI cannot tell whether the failure is pre-existing)
  AssertionError: no CUDA device is visible to this x86_64 row, which is the row that proves the delegate computes. The runner lost its GPU or the installed torch cannot reach it; either way nothing here executed.
• Build Linux CUDA Wheels / pytorch/executorch / upload / upload-manywheel-py3_10-cuda12_6 (gh) (this job did not run on the merge base, so DrCI cannot tell whether the failure is pre-existing)
  Unable to download artifact(s): Artifact not found
• Build Linux CUDA Wheels / pytorch/executorch / upload / upload-manywheel-py3_10-cuda13_0 (gh) (this job did not run on the merge base, so DrCI cannot tell whether the failure is pre-existing)
  Unable to download artifact(s): Artifact not found
• Build Linux CUDA Wheels / pytorch/executorch / upload / upload-manywheel-py3_12-cuda12_6 (gh) (this job did not run on the merge base, so DrCI cannot tell whether the failure is pre-existing)
  Unable to download artifact(s): Artifact not found
• Build Linux CUDA Wheels / pytorch/executorch / upload / upload-manywheel-py3_12-cuda13_2 (gh) (this job did not run on the merge base, so DrCI cannot tell whether the failure is pre-existing)
  Unable to download artifact(s): Artifact not found

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

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

• Apple / build-demo-ios / macos-job (gh) (trunk failure)
  RuntimeError: Command bash /Users/runner/work/_temp/exec_script failed with exit code 65

This comment was automatically generated by Dr. CI and updates every 15 minutes.

[digantdesai]

I thought we were not doing all the backends? what made you include this one?

[digantdesai]

move this to one of the previous PRs introduces cuda?

[digantdesai]

Is this also OpenVino related?