Ports: Fix dependency install when port name is not port folder name
There was a bug in the way the `.port_include.sh` script handled
installing dependencies. According to the
[documentation](https://github.com/SerenityOS/serenity/tree/master/Ports#depends)
the depends array should have port names in it. The port system allows
for the name of the port to be different from the folder where port
lives. Previously the `installdepends` function would cd to the name
of the port, now it will find and run the `package.sh` that has the
line `port=$depend` in it.