Add CI step to check changes in the exported ABI (GH-25232)

Author: pablogsal

.github/workflows/build.yml

@@ -41,6 +41,28 @@ jobs:
             git diff --name-only origin/$GITHUB_BASE_REF.. | grep -qvE '(\.rst$|^Doc|^Misc)' && echo '::set-output name=run_tests::true' || true
           fi
 
+  check_abi:
+    name: 'Check if the ABI has changed'
+    runs-on: ubuntu-20.04
+    needs: check_source
+    if: needs.check_source.outputs.run_tests == 'true'
+    steps:
+      - uses: actions/checkout@v2
+      - uses: actions/setup-python@v2
+      - name: Install Dependencies
+        run: |
+            sudo ./.github/workflows/posix-deps-apt.sh
+            sudo apt-get install -yq abigail-tools
+      - name: Build CPython
+        env:
+          CFLAGS: -g3 -O0
+        run: |
+          # Build Python with the libpython dynamic library
+          ./configure --enable-shared
+          make -j4
+      - name: Check for changes in the ABI
+        run: make check-abidump
+
   check_generated_files:
     name: 'Check if generated files are up to date'
     runs-on: ubuntu-latest