Since we are updating the install scripts, I also added the opening of the firewall for OBS on mac and windows.
I was able to test the install on windows, but was only able to test the postinstall script on mac by manually invoking it.
To test I did the following on on both OSs:

1. Output NDI from another PC (make sure firewall is off)
2. Turn on the firewall on the PC being tested
3. Run OBS
4. Create a NDI source
5. Verify the other computer cannot be selected as a source
6. Exit OBS
7. Install the DistroAV plugin
8. Run OBS
9. Select the new NDI source
10. Select Properties
11. Should be able to see, select and preview the NDI source from the other computer now

There may have been discussions on why we shouldn't do this during install. If this is not the way we want to go, I can gladly remove these commits from the PR.

Lovely 1 will review & test this in the coming weeks. This could be a good (temporary) addition, glad the script cleanitself at the end.

We need to check that this behavior does NOT trigger falseflag by anti-virus / malware as well. (can only be tested once we are in pre-release.

Tested the MacOS fix, and there is no residual postinstall script.