GH Actions: harden the workflow against PHPCS ruleset errors

If there is a ruleset error, the `cs2pr` action doesn't receive an `xml` report and exits with a `0` error code, even though the PHPCS run failed (though not on CS errors, but on a ruleset error).

This changes the GH Actions workflow to allow for that situation and still fail the build in that case.

Author: jrfnl

.github/workflows/cs.yml

@@ -34,10 +34,11 @@ jobs:
         uses: "ramsey/composer-install@v2"
 
       - name: Check PHP code style
-        continue-on-error: true
+        id: phpcs
         run: vendor/bin/phpcs --report-full --report-checkstyle=./checkstyle.xml
 
       - name: Show PHPCS results in PR
+        if: ${{ always() && steps.phpcs.outcome == 'failure' }}
         run: cs2pr ./checkstyle.xml
 
       - name: Make sure no vardumps remain