Explicitly define the libs path

Author: mxamin

.github/workflows/macosx.yml

@@ -60,6 +60,7 @@ jobs:
           echo "Working directory: $(pwd)"
           echo "libs directory listing:"
           ls -la libs || true
+          export PYXMLSEC_LIBS_DIR="$PWD/libs"
           python -m build
           rm -rf build/