Reproduction steps:
1. Open the attached project.
2. Try to build it to iOS.

Actual result:
- The build will fail when building in Xcode.

IL2CPP:
"_OpenURL", referenced from:
_ActTesterGui_OpenURL_m835977890 in Bulk_Assembly-CSharp-firstpass_0.o
(maybe you meant: __Z40Register_UnityEngine_Application_OpenURLv, __Z26Application_CUSTOM_OpenURLP12Il2CppString , _ActTesterGui_OpenURL_m835977890 , _Application_OpenURL_m2434521810 )
ld: symbol(s) not found for architecture arm64

Mono:
"_OpenURL", referenced from:
RegisterMonoModules() in RegisterMonoModules.o
(maybe you meant: __Z26Application_CUSTOM_OpenURLP10MonoString, __Z40Register_UnityEngine_Application_OpenURLv )
ld: symbol(s) not found for architecture armv7

Reproduced with:
2017.2.0b1, 2018.1.0a2

Note:
The project doesn’t move to version 2017.1, but this is most likely a regression.