Add faiss-gpu pip wheel packaging (#5131)

Summary:
Pull Request resolved: https://github.com/facebookresearch/faiss/pull/5131

Add pip wheel packaging for `faiss-gpu`, enabling `pip install faiss-gpu`
from PyPI. Builds GPU wheels for Linux x86_64, Python 3.10-3.13, with
CUDA 12.6 on manylinux_2_28.

**New files:**
- `pyproject-gpu.toml`: scikit-build-core config for faiss-gpu. Enables
  CUDA GPU support, uses Dynamic Dispatch, OpenBLAS, and excludes CUDA
  runtime libs (provided by nvidia-cuda-runtime-cu12 pip dependency).
- `.github/workflows/build-pip-gpu.yml`: CI workflow for GPU wheels using
  cibuildwheel on GPU runners (4-core-ubuntu-gpu-t4).
- `tests/test_wheel_smoke_gpu.py`: GPU smoke tests validating GPU
  detection, StandardGpuResources, GPU FlatL2/IP search, IVF+PQ on GPU,
  CPU<->GPU transfer roundtrip, and GPU serialization.

**Modified files:**
- `python/__init__.py`: Added `_preload_gpu_libs()` to pre-load CUDA
  shared libraries from pip packages before SWIG import. No-op on
  CPU-only installs.
- `.github/workflows/build.yml`: Added `build-pip-gpu` workflow call.
- `tests/BUCK`: Added `test_wheel_smoke_gpu` target for Buck CI.

Reviewed By: junjieqi

Differential Revision: D97507525

fbshipit-source-id: f8b5fa08405aa53267e791c2c0d263e2d6190741

.github/workflows/build-pip-gpu.yml

@@ -0,0 +1,97 @@
+# Copyright (c) Meta Platforms, Inc. and affiliates.
+#
+# This source code is licensed under the MIT license found in the
+# LICENSE file in the root directory of this source tree.
+
+name: Build GPU pip wheel
+
+on:
+  workflow_call:
+  workflow_dispatch:
+
+concurrency:
+  # One run per ref. Tag pushes are not cancelable — a half-canceled release
+  # build leaves PyPI in an inconsistent state. Branch/PR runs supersede.
+  group: gpu-pip-${{ github.ref }}
+  cancel-in-progress: ${{ !startsWith(github.ref, 'refs/tags/v') }}
+
+jobs:
+  build-faiss-gpu:
+    name: Build & test faiss-gpu
+    runs-on: 4-core-ubuntu-gpu-t4
+    timeout-minutes: 90
+    steps:
+      - name: Checkout
+        uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683  # v4.2.2
+
+      - name: Activate GPU pyproject.toml
+        # cibuildwheel + scikit-build-core both require literal pyproject.toml.
+        # Workspace is fresh per job (actions/checkout creates new tree).
+        run: cp pyproject-gpu.toml pyproject.toml
+
+      - name: Set up Python
+        # Pin host Python explicitly: the 4-core-ubuntu-gpu-t4 runner image
+        # ships a broken Python 3.14.4 in its tool cache (libpython3.14.so.1.0
+        # missing), and pypa/cibuildwheel picks that up by default.
+        uses: actions/setup-python@a26af69be951a213d495a4c3e4e4022e16d87065  # v5.6.0
+        with:
+          python-version: '3.12'
+
+      - name: Build wheel (cibuildwheel)
+        uses: pypa/cibuildwheel@ee02a1537ce3071a004a6b08c41e72f0fdc42d9a  # v3.4.0
+        env:
+          CIBW_BUILD_VERBOSITY: 1
+
+      - name: Upload wheel
+        if: always()
+        uses: actions/upload-artifact@ea165f8d65b6e75b540449e92b4886f43607fa02  # v4.6.2
+        with:
+          name: wheels-gpu
+          path: wheelhouse/*.whl
+
+  publish-gpu:
+    name: Publish faiss-gpu to PyPI
+    needs: [build-faiss-gpu]
+    runs-on: ubuntu-latest
+    if: github.event_name == 'push' && startsWith(github.ref, 'refs/tags/v')
+    environment:
+      name: pypi
+      url: https://pypi.org/p/faiss-gpu
+    permissions:
+      id-token: write
+      contents: read
+    steps:
+      - name: Download wheel
+        uses: actions/download-artifact@65a9edc5881444af0b9093a5e628f2fe47ea3b2e  # v4.1.7
+        with:
+          name: wheels-gpu
+          path: dist
+      - name: Publish to PyPI
+        uses: pypa/gh-action-pypi-publish@76f52bc884231f62b9a034ebfe128415bbaabdfc  # release/v1
+        with:
+          verbose: true
+          attestations: false
+
+  publish-testpypi-gpu:
+    name: Publish faiss-gpu to TestPyPI
+    needs: [build-faiss-gpu]
+    runs-on: ubuntu-latest
+    if: github.event_name == 'workflow_dispatch'
+    environment:
+      name: testpypi
+      url: https://test.pypi.org/p/faiss-gpu
+    permissions:
+      id-token: write
+      contents: read
+    steps:
+      - name: Download wheel
+        uses: actions/download-artifact@65a9edc5881444af0b9093a5e628f2fe47ea3b2e  # v4.1.7
+        with:
+          name: wheels-gpu
+          path: dist
+      - name: Publish to TestPyPI
+        uses: pypa/gh-action-pypi-publish@76f52bc884231f62b9a034ebfe128415bbaabdfc  # release/v1
+        with:
+          repository-url: https://test.pypi.org/legacy/
+          skip-existing: true
+          verbose: true

.github/workflows/build.yml

@@ -17,3 +17,5 @@ jobs:
     if: github.event_name == 'push' && startsWith(github.ref, 'refs/tags/v')
   build-pip:
     uses: ./.github/workflows/build-pip.yml
+  build-pip-gpu:
+    uses: ./.github/workflows/build-pip-gpu.yml