build: fix the pypy wheel arguments

This happened:

```
  ********************************************************************************
  The arguments ['--python-tag', 'pp38.pp39.pp310'] were given via `--global-option`.
  Please use `--build-option` instead,
  `--global-option` is reserved for flags like `--verbose` or `--quiet`.

  This deprecation is overdue, please update your project and remove deprecated
  calls to avoid build errors in the future.
  ********************************************************************************
```

Author: nedbat

.github/workflows/kit.yml

@@ -232,10 +232,13 @@ jobs:
           pypy3 -m pip install -r requirements/kit.pip
 
       - name: "Build wheel"
+        env:
+          DIST_EXTRA_CONFIG: extra.cfg
         run: |
           # One wheel works for all PyPy versions. PYVERSIONS
           # yes, this is weird syntax: https://github.com/pypa/build/issues/202
-          pypy3 -m build -w -C="--global-option=--python-tag" -C="--global-option=pp38.pp39.pp310"
+          echo -e "[bdist_wheel]\npython_tag=pp38.pp39.pp310" > $DIST_EXTRA_CONFIG
+          pypy3 -m build -w
 
       - name: "List wheels"
         run: |