Steps to reproduce:
1. Open User's attached project
2. Build for iOS
3. Open XCode
4. Build for selected Apple device (iPhone or iPad)

Result: Build fails due to the fallowing error in XCode:
RegisterMonoModules.cpp:3290:16: Use of undeclared identifier 'Unity'
RegisterMonoModules.cpp:3295:16: Use of undeclared identifier 'UI'
RegisterMonoModules.cpp:3302:16: Use of undeclared identifier 'UI'
RegisterMonoModules.cpp:3311:16: Use of undeclared identifier 'UI'
RegisterMonoModules.cpp:3314:16: Use of undeclared identifier 'UI'
RegisterMonoModules.cpp:3314:16: Use of undeclared identifier 'TextRendering'

Reproduced with: 5.6.0b3, 5.5.0p3
Not reproduced with: 5.4.3p3 (due to errors in the Console in Unity)

Note:
Build is successful for Android. The issue only appears in XCode.