Use environment variable for pipx

Author: abravalheri

.github/workflows/main.yml

@@ -90,15 +90,16 @@ jobs:
         if: steps.cache.outputs.cache-hit != 'true'
         working-directory: setuptools/tests/config
         run: python -m downloads.preload setupcfg_examples.txt
+      - name: Adjust env vars
+        shell: bash
+        run: |
+          echo 'PIPX_DEFAULT_PYTHON=${{ steps.python-install.outputs.python-path }}' >> $GITHUB_ENV
       - name: Pre-build distributions for test
         shell: bash
         run: |
           rm -rf dist
           # workaround for pypa/setuptools#4333
-          pipx run \
-            --python ${{ steps.python-install.outputs.python-path }} \
-            --pip-args 'pyproject-hooks!=1.1' \
-            build
+          pipx run --pip-args 'pyproject-hooks!=1.1' build
           echo "PRE_BUILT_SETUPTOOLS_SDIST=$(ls dist/*.tar.gz)" >> $GITHUB_ENV
           echo "PRE_BUILT_SETUPTOOLS_WHEEL=$(ls dist/*.whl)" >> $GITHUB_ENV
           rm -rf setuptools.egg-info  # Avoid interfering with the other tests