Steps:
1. Create a New Project
2. Player Settings > Other Settings > Scripting Backend > IL2CPP
3. Build for Standalone

Result: build fails. The following errors are shown:
[...]
il2cpp.exe didn't catch exception: System.InvalidOperationException: C++ code builder is unable to build C++ code. Please ensure the macOS SDK is installed in one of the following directories:
[...]
Exception: /Volumes/LukasAHDD/Applications/2018.3/Unity 2018.3.0b5_01088ee0a3a8/Unity.app/Contents/il2cpp/build/il2cppcore/il2cppcore.dll did not run properly! [...]
UnityEditor.BuildPlayerWindow+BuildMethodException: 3 errors

Reproduced with: 2018.3.0b5, 2019.1.0a4.
Not reproduced with: 2018.2.12f1.

Note:
-build works as expected on Windows.