fix: update clang++ version in build step to llvm@18 to match macos-latest

Author: yoyolicoris

.github/workflows/python-package.yml

@@ -77,7 +77,7 @@ jobs:
         flake8 . --count --exit-zero --max-complexity=10 --max-line-length=127 --statistics
     - name: Build CPP extension with clang++
       run: |
-        export CXX=$(brew --prefix llvm@15)/bin/clang++
+        export CXX=$(brew --prefix llvm@18)/bin/clang++
         export LDFLAGS="-L/usr/local/opt/libomp/lib"
         export CPPFLAGS="-I/usr/local/opt/libomp/include"
         pip install -e .[dev]