iOS Simulator doesn't have any WebKit system feature flags
Created attachment 434435 [details] Patch
<rdar://problem/80991854>
Confirmed with a production build that the plist goes into the right place.
Committed r280397 (240038@main): <https://commits.webkit.org/240038@main> All reviewed patches have been landed. Closing bug and clearing flags on attachment 434435 [details].