I'm trying at add iMessage stickers to an Unreal Engine 4 based game.
Due to the way UE4 builds .IPA files, I'm approaching this by making a pure, stand-alone Xcode project for a simple iOS app with a stickers extension. This project can be submitted to TestFlight, and the auto-scan accepts it and it can be downloaded by testers.
I then extract the sticker extension from this .IPA, and manually add it to our game's .IPA, fixing up various version numbers and other .plist entries using PListBuddy. I also re-sign the PlugIns extension (with entitlements), the main app (with entitlements), and finally re-sign the .IPA itself.
After submitting to TestFlight, I get an email reply saying there was one error:
"The binary is invalid - The LC_ENCRYPTION_INFO load command is not expected for the bundle executable of MyMobile.app. This binary does not seem to have been built with Apple's linker."
The few other posts that mention this specific error seem to be from years ago and the developer(s) were using pre-release tools before stickers were officially supported. This is not my case, I am using the released Xcode 10.1 for all my builds and Xcode 10.2's Application Loader.
Also, all my manual futzing with the unzipping, re-signing, re-zipping seems to pass the TestFlight auto-scan and the game can be downloaded by testers when I leave out the stickers extension.
Is there anyone else who's added stickers to a UE4 project that could share how they did it?
Is there any documentation I've overlooked as to what this error means, and what I might be doing to cause it?
I don't suppose hope-against-hope that there's anyone at Apple that might come across this post that could give any insight as to what I might be doing to make the TestFlight auto-scan flag this?