This is a Python version of the existing `make_source_archive.sh`
script. IMO it's easier to read, and it'll also be easier to extend with
the necessary functionality for D10598.
The number of lines of code is larger than `make_source_archive.sh`, but
it has considerably less invocations of `awk` ;-) And also the filtering
is integrated, instead of forking out to Python to prevent certain files
to be included in the tarball.
Reviewed By: dfelinto, campbellbarton
Differential Revision: https://developer.blender.org/D10629
