add github workflow for test-pypi cross-OS wheel builds

Author: AlePalu

.github/workflows/testpypi-macos.yml

@@ -32,11 +32,12 @@ jobs:
 
       - name: Build wheels
         run: |
-          echo "CC=$(brew --prefix llvm@20)/bin/clang" >> $GITHUB_ENV
-          echo "CXX=$(brew --prefix llvm@20)/bin/clang++" >> $GITHUB_ENV
           python -m cibuildwheel --output-dir wheelhouse
         env:
           CIBW_BUILD: "cp311-*"
+          CIBW_ENVIRONMENT: >
+            CC=$(brew --prefix llvm@20)/bin/clang
+            CXX=$(brew --prefix llvm@20)/bin/clang++
 
       - name: Upload to TestPyPI
         run: |