Since Facebook SDK 7.0.0, their iOS SDK requires the project to contain at least one ".swift" file. Otherwise the build fails due to missing Swift standard libraries. And although Titanium already enables Swift for module compatibility, it does not seem to be enough so far.
The same issue is happening for other app frameworks like React Native and they workaround it by adding it to the Xcode project (which is not generated their but stable, an option Titanium has not).
Importance of the Facebook SDK 7+ upgrade: They fixed an issue with random server errors crashing the whole app that uses it, therefore it's a critical update developers should perform.