Reproduction Steps:
1. Open "Case793420" project
2. Enter valid Player Settings > Automatic Signing TeamID
3. Enter valid Player Settings > Bundle Identifier
4. Build to iOS platform
5. Open the generated Xcode project in Xcode
6. Build the project in Xcode
7. Notice the compilation errors on two lines in UnityViewControllerBase+iOS.h

User suggested fix:
1. In Xcode, open the file UnityViewControllerBase+iOS.h
2. Replace the two lines with compilation errors with the code below

#ifdef __cplusplus
extern "C" {
#endif
void AddViewControllerRotationHandling(Class class_, IMP willRotateToInterfaceOrientation, IMP didRotateFromInterfaceOrientation, IMP viewWillTransitionToSize);
void AddViewControllerDefaultRotationHandling(Class class_);
#ifdef __cplusplus
}
#endif

Expected behaviour: Project builds correctly without any errors.

Reproduced on versions: Unity 2017.1.3f1, 2017.2.1p2, 2017.3.0p3, 2018.1.0b3
Reproduced on devices: iPhone 7 Plus iOS 10.3.2
Reproduced on Xcode 9.0