Limit tests for stdlib distutils to one job.

.github/workflows/main.yml

@@ -11,7 +11,6 @@ jobs:
     strategy:
       matrix:
         distutils:
-        - stdlib
         - local
         python:
         - pypy-3.7
@@ -23,6 +22,10 @@ jobs:
         - ubuntu-latest
         - macos-latest
         - windows-latest
+        include:
+        - platform: ubuntu-latest
+          python: "3.10"
+          distutils: stdlib
     runs-on: ${{ matrix.platform }}
     env:
       SETUPTOOLS_USE_DISTUTILS: ${{ matrix.distutils }}
@@ -46,14 +49,7 @@ jobs:
             ${{ matrix.python }}
 
   test_cygwin:
-    strategy:
-      matrix:
-        distutils:
-        - stdlib
-        - local
     runs-on: windows-latest
-    env:
-      SETUPTOOLS_USE_DISTUTILS: ${{ matrix.distutils }}
     steps:
       - uses: actions/checkout@v2
       - name: Install Cygwin with Python
@@ -76,11 +72,6 @@ jobs:
           tox -- --cov-report xml
 
   integration-test:
-    strategy:
-      matrix:
-        distutils:
-        - stdlib
-        - local
     needs: test
     if: github.event_name == 'workflow_dispatch' || (github.event_name == 'push' && contains(github.ref, 'refs/tags/'))
     # To avoid long times and high resource usage, we assume that:
@@ -91,8 +82,6 @@ jobs:
     #    "integration")
     # With that in mind, the integration tests can run for a single setup
     runs-on: ubuntu-latest
-    env:
-      SETUPTOOLS_USE_DISTUTILS: ${{ matrix.distutils }}
     steps:
       - uses: actions/checkout@v2
       - name: Install OS-level dependencies