How to mount folder for custom docker image in Azure App Service for Linux?

Question

Microsoft Azure

In the usual creation of a web application, for deployment it is enough to copy the files to the /site/wwwroot folder , but how to achieve the same behavior when creating a custom image?
In the off repository https://github.com/Azure-App-Service/php/blob/mast... there is a line:
ln -s /home/site/wwwroot /var/www/html
when I try to do this, nothing comes out.
Here is an example of my Dockerfile:

FROM php:7.0.6-apache
RUN ln -s /home/site/wwwroot /var/www/html
CMD ["apache2-foreground"]

I need that when copying to /home/site/wwwroot they are launched in the docker way.