Use 7zip to extract tar files on platforms that support symlinks

Summary:
7z is much faster in extracting archives than the build in python functions.
This requires a support for symlinks.

With the build in unpack function its basically impossible to extract oxygen-icons5 as it takes ages.

Test Plan: Tested on Windows and Linux with oxygen-icons5 and openssl

Reviewers: kfunk, arrowdodger

Reviewed By: kfunk

Subscribers: Windows

Differential Revision: https://phabricator.kde.org/D5642