Fix missing slash in multiline command

Author: e1himself

.github/workflows/test.yml

@@ -26,10 +26,8 @@ jobs:
           composer install $COMPOSER_FLAGS
 
       - name: Test
-        env:
-          ERROR_REPORTING: 24567 # E_ALL & ~ E_DEPRECATED & ~ E_NOTICE
         run: |
-          php -d error_reporting=$ERROR_REPORTING
+          php -d error_reporting=$(php -r 'echo E_ALL & ~ E_DEPRECATED & ~ E_NOTICE;') \
               -d xdebug.mode=coverage \
               -d xdebug.overload_var_dump=0 \
               vendor/bin/phpunit