Use llvm@18 to fix build issue.

Author: rkistner

.github/actions/build-wasm/action.yml

@@ -18,7 +18,7 @@ runs:
       shell: bash
       run: |
         brew install cmake
-        brew install llvm
+        brew install llvm@18
         brew install binaryen
         curl -sL https://github.com/WebAssembly/wasi-sdk/releases/download/wasi-sdk-22/libclang_rt.builtins-wasm32-wasi-22.0.tar.gz | \
         tar x -zf - -C /opt/homebrew/opt/llvm/lib/clang/18*