Access __file__ global in Early bind function (package.py)

[vanridal]

Sometimes it can be quite useful to access the location of a package file in a Early bind function
Maybe you want to find a relative file to read in, like a python requirments.txt or a VERSION token file

In the global preprocess, the DeveloperPackage object as a filepath attribute,
Unfortunately in Early bind function the this object does not, I thought to add the attribute to the this object but then this will add this path attribute to the built package file, which i think is undesirable.

I think the best option is to support the standard global variable __file__

As this will not be added to the final build package file