Default to local distutils unless specified. Fixes #3726.

Author: jaraco

.github/workflows/main.yml

@@ -45,8 +45,6 @@ jobs:
   test:
     strategy:
       matrix:
-        distutils:
-        - local
         python:
         - "3.7"
         # disabled due to #3365
@@ -68,13 +66,14 @@ jobs:
           platform: ubuntu-latest
         - python: pypy3.9
           platform: ubuntu-latest
+          distutils: stdlib
         - platform: ubuntu-latest
           python: "3.10"
           distutils: stdlib
     runs-on: ${{ matrix.platform }}
     continue-on-error: ${{ matrix.python == '3.12' }}
     env:
-      SETUPTOOLS_USE_DISTUTILS: ${{ matrix.distutils }}
+      SETUPTOOLS_USE_DISTUTILS: ${{ matrix.distutils || 'local' }}
     timeout-minutes: 75
     steps:
       - uses: actions/checkout@v3