ci: Rename cirrus.sh to more general ci.sh

This makes sense in the process of moving stuff to GitHub Actions.

.github/workflows/ci.yml

@@ -98,7 +98,7 @@ jobs:
           tag: linux-debian-image
           command: >
             git config --global --add safe.directory ${{ github.workspace }} &&
-            ./ci/cirrus.sh
+            ./ci/ci.sh
 
       - run: cat tests.log || true
         if: ${{ always() }}
@@ -156,7 +156,7 @@ jobs:
 
       - name: CI script
         env: ${{ matrix.env_vars }}
-        run: ./ci/cirrus.sh
+        run: ./ci/ci.sh
 
       - run: cat tests.log || true
         if: ${{ always() }}