Link output of CSS eslinting on GitLab correctly

@spokje
I didn't realise the Styleint Error has already been resolved and only the linking of CSS output is not correct.
Reverted the changes on MR.

I've checked that updated stylelint-formatter: gitlab-formatters/stylelint-formatter-gitlab is already in there..

Hence please move it into correct state...

Tried to clarify the IS, since there seems to be a lot of misunderstanding of what we're trying to accomplish in this issue.

I think it's because of this at the start of the job

$ mkdir /build;
$ cp -Ria $CI_PROJECT_DIR/* /build/
$ cd /build

The paths are relative to the original directory instead of /build - it would be better if we could just run the linter in place?