Add check in workflows to test for "php -i > /dev/null" to be empty

[DracoBlue]

Current

docker run --rm  --entrypoint php exozet/php-fpm:8.0.6-sudo-alpine -- -i > /dev/null

returns:

PHP Warning:  PHP Startup: Unable to load dynamic library 'imagick' (tried: /usr/local/lib/php/extensions/no-debug-non-zts-20200930/imagick (Error loading shared library /usr/local/lib/php/extensions/no-debug-non-zts-20200930/imagick: No such file or directory), /usr/local/lib/php/extensions/no-debug-non-zts-20200930/imagick.so (Error loading shared library libgomp.so.1: No such file or directory (needed by /usr/local/lib/php/extensions/no-debug-non-zts-20200930/imagick.so))) in Unknown on line 0```

which is a warning because a dependency for imagick is missing. We could have spotted this easily if we would have checked for warnings.