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/test.yml

@@ -143,11 +143,11 @@ jobs:
 
       - name: 'PHPCS: check code style to show results in PR'
         if: ${{ matrix.custom_ini == false && matrix.php == '7.4' }}
-        continue-on-error: true
+        id: phpcs
         run: php bin/phpcs --no-cache --parallel=1 --report-full --report-checkstyle=./phpcs-report.xml
 
       - name: Show PHPCS results in PR
-        if: ${{ matrix.custom_ini == false && matrix.php == '7.4' }}
+        if: ${{ always() && steps.phpcs.outcome == 'failure' && matrix.php == '7.4' }}
         run: cs2pr ./phpcs-report.xml
 
       - name: Download the PHPCS phar