Add ad hoc MLX EP conformance validation

Author: Gopalakrishnan Nallasamy

.github/workflows/ad_hoc_mlx_ep_conformance.yml

@@ -0,0 +1,102 @@
+name: Ad hoc MLX EP conformance for PR 28968
+
+on:
+  push:
+    branches:
+      - ad-hoc-mlx-conformance-28968-20260717
+
+permissions:
+  contents: read
+
+jobs:
+  mlx-ep-conformance:
+    name: MLX plugin EP shared invariants (macOS arm64)
+    runs-on: macos-14
+    timeout-minutes: 180
+
+    steps:
+      - uses: actions/checkout@v6
+
+      - uses: actions/setup-python@v6
+        with:
+          python-version: "3.12"
+
+      - name: Install build and MLX plugin dependencies
+        run: |
+          set -euo pipefail
+          brew install ninja
+          python -m pip install --upgrade pip
+          python -m pip install --no-deps "onnxruntime-ep-mlx==0.3.0"
+          python - <<'PY'
+          import onnxruntime_ep_mlx as mlx
+          print("MLX EP version:", mlx.version())
+          print("MLX EP name:", mlx.ep_name())
+          print("MLX EP library:", mlx.library_path())
+          PY
+
+      - name: Build onnxruntime_provider_test from PR 28968
+        run: |
+          set -euo pipefail
+          python tools/ci_build/build.py \
+            --build_dir build/mlx-conformance \
+            --config Release \
+            --update \
+            --build \
+            --parallel \
+            --target onnxruntime_provider_test \
+            --cmake_generator Ninja
+
+      - name: Run shared conformance invariants against MLX
+        run: |
+          set -euo pipefail
+          MLX_LIB="$(python -c 'import onnxruntime_ep_mlx as mlx; print(mlx.library_path())')"
+          MLX_DIR="$(dirname "$MLX_LIB")"
+          TEST_BIN="$(find build/mlx-conformance -type f -name onnxruntime_provider_test -perm -111 | head -n 1)"
+
+          test -n "$TEST_BIN"
+          test -x "$TEST_BIN"
+          test -f "$MLX_LIB"
+
+          echo "Test binary: $TEST_BIN"
+          echo "MLX plugin: $MLX_LIB"
+          otool -L "$MLX_LIB"
+
+          export DYLD_LIBRARY_PATH="$MLX_DIR:${DYLD_LIBRARY_PATH:-}"
+          export ORT_UNIT_TEST_MAIN_DYNAMIC_PLUGIN_EP_CONFIG_JSON="$(python - "$MLX_LIB" <<'PY'
+          import json
+          import sys
+
+          print(json.dumps({
+              "ep_library_registration_name": "MLXExecutionProvider",
+              "ep_library_path": sys.argv[1],
+              "selected_ep_name": "MLXExecutionProvider",
+          }))
+          PY
+          )"
+
+          "$TEST_BIN" \
+            --gtest_filter='EpPluginConformanceTest.*' \
+            --gtest_color=no \
+            2>&1 | tee mlx_ep_conformance.log
+
+      - name: Publish test summary
+        if: always()
+        run: |
+          {
+            echo "### MLX plugin EP conformance"
+            echo '```text'
+            if test -f mlx_ep_conformance.log; then
+              tail -n 80 mlx_ep_conformance.log
+            else
+              echo "Conformance test did not produce a log."
+            fi
+            echo '```'
+          } >> "$GITHUB_STEP_SUMMARY"
+
+      - name: Upload conformance log
+        if: always()
+        uses: actions/upload-artifact@v6
+        with:
+          name: mlx-ep-conformance-log
+          path: mlx_ep_conformance.log
+          if-no-files-found: warn