Update DataStore directory on macOS

[ismailmustafa]

The default save location for the datafile is in the documents directory. This works fine on iOS since it's sandboxed, however, for non-sandboxed applications running on macOS, this results in the following popup showing up:

This MR addresses two things:

1. Changes the data file save location on macOS to be the caches directory. This directory does not require user permission. It is also the directory in which downloadable files should be saved as per Apple's guidelines.
2. Fixes a compilation error on the macOS target caused by a newly added file that was not added to the macOS target.

[jaeopt]

LGTM