Add an actions job for capturing compile commands on all platforms (#11)

This should help to make flags and options more comparable between
Bazel and CMake.

.github/workflows/capture-compile-commands.yaml

@@ -0,0 +1,54 @@
+name: Extract nanobind_example compile commands for CMake and Bazel
+
+on:
+  workflow_dispatch:
+
+jobs:
+  nb-compile-commands:
+    name: Capture nanobind CMake compile commands on ${{ matrix.os }}
+    runs-on: ${{ matrix.os }}
+    strategy:
+      fail-fast: false
+      matrix:
+        os: [ ubuntu-latest, macos-latest, windows-latest ]
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          repository: wjakob/nanobind_example
+          fetch-depth: 0
+      - name: Set up Python and dependencies
+        uses: actions/setup-python@v5
+        with:
+          python-version: 3.12
+      - run: python -m pip install --upgrade build
+      - name: Build and capture CMake compile commands
+        run: python -m build . --wheel -Ccmake.args=-DCMAKE_EXPORT_COMPILE_COMMANDS=ON
+      - name: Upload commands and Ninja build artifacts
+        uses: actions/upload-artifact@v4
+        with:
+          name: compile-commands-${{ matrix.os}}-cmake
+          path: |
+            # the build subfolder name is autogenerated, so just use a glob.
+            build/cp312-*/build.ninja  # this has the linker command section. 
+            build/cp312-*/CMakeCache.txt
+            build/cp312-*/compile_commands.json
+          if-no-files-found: error
+      - name: Clean repo and switch to Bazel
+        run: git clean -xdf && git checkout bazel
+      - name: Extract Bazel compile commands for ${{ matrix.os}}
+        run: |
+          bazel run @hedron_compile_commands//:refresh_all \
+            -- \
+            --compilation_mode=opt \
+            --cxxopt=-std=c++17 \
+            --@rules_python//python/config_settings:python_version=3.12 \
+            --@nanobind_bazel//:minsize \
+            --@nanobind_bazel//:py-limited-api=cp312
+      - name: Upload Bazel compile commands and flag files for ${{ matrix.os }}
+        uses: actions/upload-artifact@v4
+        with:
+          name: compile-commands-${{ matrix.os}}-bazel
+          path: |
+            compile_commands.json
+            bazel-out/*-opt/**/*.params  # these should be two - the libnanobind params, and the nanobind_example_ext params.
+          if-no-files-found: error