Use LLVM-18 on macOS Intel

.github/workflows/ci.yml

@@ -93,8 +93,8 @@ jobs:
       - name: Download LLVM (MacOS Intel)
         if: matrix.os == 'macos-13'
         run: |
-          brew install llvm@20 [email protected]
-          echo "/usr/local/opt/llvm@20/bin" >> $GITHUB_PATH
+          brew install llvm@18 [email protected]
+          echo "/usr/local/opt/llvm@18/bin" >> $GITHUB_PATH
 
       - name: Download LLVM (MacOS ARM)
         if: matrix.os == 'macos-14'