There was even a case recently where a man won a lawsuit because he was excluded by a clothing store that was searching for a female employee for doing an inventory job.
"Brussels, 23 August 2018 - The legal action taken by the Institute for Equality of Women and Men reminds employers that sex is not a criterion for refusing an application. The Leuven Labor Court has sentenced a clothing store to discrimination based on sex. He refused a man's candidacy because he wanted to hire a woman."
https://presscenter.org/nl/pressrelease/20180822/een-sollici... (dutch) https://presscenter.org/nl/pressrelease/20180822/een-sollici... (french)
That being said I also seen adverts asking for women but technically it's against the law and even with all those laws discriminations happen more often than not.