Fix ccache for GPU, Metal, and Windows CI builds

Summary:
Fix ccache configuration to actually achieve cache hits across CI runs:

1. (P0) Configure ccache sloppiness for CUDA/ROCm builds — without `hash_dir=false` and relaxed sloppiness settings, nvcc/hipcc absolute paths cause 100% cache misses even when source is unchanged.
2. (P1) Add missing `-DCMAKE_C_COMPILER_LAUNCHER=ccache -DCMAKE_CXX_COMPILER_LAUNCHER=ccache` to the Metal build step, which had its own cmake invocation that was missed in D102926935.
3. (P2) Increase cache size from 2G to 4G for GPU builds since CUDA object files are significantly larger.
4. (P3) Add ccache to the Windows build in build-pull-request.yml, which uses inline build steps instead of the build_cmake composite action.

Differential Revision: D103482603

Author: Michael Norris

.github/actions/build_cmake/action.yml

@@ -168,8 +168,14 @@ runs:
       uses: hendrikmuhs/ccache-action@v1
       with:
         key: ${{ runner.os }}-${{ runner.arch }}-${{ inputs.opt_level }}-gpu${{ inputs.gpu }}-cuvs${{ inputs.cuvs }}-rocm${{ inputs.rocm }}-svs${{ inputs.svs }}
-        max-size: 2G
+        max-size: ${{ inputs.gpu == 'ON' && '4G' || '2G' }}
         update-package-index: true
+    - name: Configure ccache for CUDA/ROCm
+      if: inputs.gpu == 'ON'
+      shell: bash
+      run: |
+        ccache --set-config=sloppiness=pch_defines,time_macros,include_file_mtime,include_file_ctime
+        ccache --set-config=hash_dir=false
     - name: Setup macOS Metal environment
       if: inputs.metal == 'ON'
       shell: bash
@@ -209,6 +215,8 @@ runs:
               -DFAISS_ENABLE_PYTHON=OFF \
               -DBUILD_TESTING=ON \
               -DCMAKE_BUILD_TYPE=Release \
+              -DCMAKE_C_COMPILER_LAUNCHER=ccache \
+              -DCMAKE_CXX_COMPILER_LAUNCHER=ccache \
               -DCMAKE_PREFIX_PATH="$(brew --prefix libomp)" \
               .
         cmake --build build --target faiss_metal TestMetalIndexFlat -j$(sysctl -n hw.logicalcpu)

.github/workflows/build-pull-request.yml

@@ -201,6 +201,11 @@ jobs:
         run: |
           conda install -y -q cmake swig "numpy>=2.0,<3.0" scipy pytest gflags setuptools
           conda install -y -q mkl=2024.2.2 mkl-devel=2024.2.2
+      - name: Setup ccache
+        uses: hendrikmuhs/ccache-action@v1
+        with:
+          key: ${{ runner.os }}-${{ runner.arch }}-dd-gpuOFF
+          max-size: 2G
       - name: Build
         shell: pwsh
         run: |
@@ -217,6 +222,8 @@ jobs:
             -DFAISS_ENABLE_C_API=OFF `
             -DBLA_VENDOR=Intel10_64_dyn `
             -DCMAKE_BUILD_TYPE=Release `
+            -DCMAKE_C_COMPILER_LAUNCHER=ccache `
+            -DCMAKE_CXX_COMPILER_LAUNCHER=ccache `
             -DPython_ROOT_DIR="$pythonDir" `
             .
           # Add faiss.dll and dependency DLLs to PATH for GoogleTest discovery