Install MLIR in CI step

Author: gf712

.github/workflows/premerge.yml

@@ -19,6 +19,7 @@ jobs:
         wget https://apt.llvm.org/llvm.sh
         chmod +x llvm.sh
         sudo ./llvm.sh 20 all
+        sudo apt install mlir
 
     - name: Configure CMake
       run: cmake -B ${{github.workspace}}/build -DCMAKE_BUILD_TYPE=${{env.BUILD_TYPE}}