List of steps to reproduce (step by step, including full links if applicable):

• Follow https://gerrit.wikimedia.org/r/plugins/gitiles/mediawiki/core/+/master/DEVELOPERS.md until docker-compose up -d
• run docker-compose exec mediawiki /bin/bash
• php --info | grep xdebug outputs

/etc/php/7.2/cli/conf.d/20-xdebug.ini

What happens?:

• However php -r "printf('xDebug does%s exists.' . PHP_EOL, extension_loaded('xdebug') ? '' : 'n\'t');" says

php -r "printf('xDebug does%s exists.' . PHP_EOL, extension_loaded('xdebug') ? '' : 'n\'t');"
xDebug doesn't exists.

• Also phpstorm cannot discover xdebug and thus debugging is not enabled which is very helpful for developing

What should have happened instead?:

• It should say xdebug does exists and PHP Storm should find it

Software version (if not a Wikimedia wiki), browser information, screenshots, other information, etc:

latest master versions

echo $XDEBUG_ENABLE says true

and the x-dbug.ini is empty and is not a symlink as I would have expected
`ls -lah /etc/php/7.2/cli/conf.d/20-xdebug.ini
-rw-r--r-- 1 1000 root 0 Jan 12 21:49 /etc/php/7.2/cli/conf.d/20-xdebug.ini