Error compiling ios 11.3 on xcode 9.3

[erikparr]

Error compiling ios 11.3 on xcode 9.3, Unity 2018.1.2f1

Undefined symbols for architecture arm64:
  "__forceToSpeaker", referenced from:
      _iPhoneSpeaker__forceToSpeaker_m3710460793 in Bulk_Assembly-CSharp_0.o
      _iPhoneSpeaker_ForceToSpeaker_m4129981170 in Bulk_Assembly-CSharp_0.o
      _ExampleProject_TrackableEventHandler_Start_m2478629829 in Bulk_Assembly-CSharp_0.o
     (maybe you meant: _iPhoneSpeaker__forceToSpeaker_m3710460793)
ld: symbol(s) not found for architecture arm64
clang: error: linker command failed with exit code 1 (use -v to see invocation)