fix CI (hopefully)

.github/actions/prepare-mlir-cache/action.yml

@@ -0,0 +1,54 @@
+name: Prepare MLIR Cache
+description: Restore or build the cached MLIR toolchain.
+
+inputs:
+  llvm-commit:
+    description: LLVM commit to build.
+    required: true
+  mold-linker-flags:
+    description: Linker flags used to force mold.
+    required: true
+
+runs:
+  using: composite
+  steps:
+    - name: Restore MLIR cache
+      id: restore-mlir-cache
+      uses: actions/cache/restore@v4
+      with:
+        path: onnx-mlir/llvm-project
+        key: mlir-${{ runner.os }}-${{ inputs.llvm-commit }}
+
+    - name: Clone LLVM
+      if: steps.restore-mlir-cache.outputs.cache-hit != 'true'
+      shell: bash
+      run: |
+        git clone --filter=blob:none --no-checkout https://github.com/llvm/llvm-project.git onnx-mlir/llvm-project
+        cd onnx-mlir/llvm-project
+        git fetch --depth 1 origin ${{ inputs.llvm-commit }}
+        git checkout FETCH_HEAD
+
+    - name: Build MLIR
+      if: steps.restore-mlir-cache.outputs.cache-hit != 'true'
+      shell: bash
+      run: |
+        cmake -S onnx-mlir/llvm-project/llvm -B onnx-mlir/llvm-project/build -G Ninja \
+          -DLLVM_ENABLE_PROJECTS="mlir;clang" \
+          -DLLVM_ENABLE_RUNTIMES="openmp" \
+          -DLLVM_TARGETS_TO_BUILD="host" \
+          -DCMAKE_BUILD_TYPE=Release \
+          -DLLVM_ENABLE_ASSERTIONS=ON \
+          -DLLVM_ENABLE_RTTI=ON \
+          -DENABLE_LIBOMPTARGET=OFF \
+          -DLLVM_ENABLE_LIBEDIT=OFF \
+          -DCMAKE_EXE_LINKER_FLAGS="${{ inputs.mold-linker-flags }}" \
+          -DCMAKE_SHARED_LINKER_FLAGS="${{ inputs.mold-linker-flags }}" \
+          -DCMAKE_MODULE_LINKER_FLAGS="${{ inputs.mold-linker-flags }}"
+        cmake --build onnx-mlir/llvm-project/build
+
+    - name: Save MLIR cache
+      if: steps.restore-mlir-cache.outputs.cache-hit != 'true'
+      uses: actions/cache/save@v4
+      with:
+        path: onnx-mlir/llvm-project
+        key: mlir-${{ runner.os }}-${{ inputs.llvm-commit }}