Use pythonpath

Author: mxamin

.github/workflows/manylinux.yml

@@ -48,24 +48,22 @@ jobs:
           GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
           PY_ABI: ${{ matrix.python-abi }}
           MANYLINUX_IMAGE: ${{ matrix.image }}
-          LIBXML2_VERSION: ${{ env.LIBXML2_VERSION }}
-          LIBXSLT_VERSION: ${{ env.LIBXSLT_VERSION }}
         run: |
           set -euxo pipefail
           docker run --rm \
             -v "$PWD:$PWD" \
             -w "$PWD" \
             -e GH_TOKEN \
             -e PYXMLSEC_STATIC_DEPS \
-            -e LIBXML2_VERSION \
-            -e LIBXSLT_VERSION \
             -e PY_ABI \
             -e MANYLINUX_IMAGE \
             -e HOST_UID="$(id -u)" \
             -e HOST_GID="$(id -g)" \
             "quay.io/pypa/${MANYLINUX_IMAGE}" \
             sh -lc '
               set -eu
+              # Make local build helpers importable for isolated PEP 517 backend subprocesses.
+              export PYTHONPATH="$PWD${PYTHONPATH:+:${PYTHONPATH}}"
 
               # Step: Install system build dependencies (manylinux only)
               echo "== [container] Step: Install system build dependencies (manylinux only) =="