CI: install build in the release job, needed to create sdist

Author: rgommers

.github/workflows/wheel_tests_and_release.yml

@@ -198,7 +198,7 @@ jobs:
         run: |
           python -m pip install --upgrade pip
           pip install twine
-          pip install cython numpy
+          pip install cython numpy build
       
       - uses: actions/download-artifact@v3
         id: download