Steps To Reproduce:

1. Create a new project
2. File > Build Settings > Build

Expected Result: It should build successfully

Observed Result: Build Fails with an exception.

Reproducible on: 2019.2.0a7 (d06a032e8889)

Not Reproducible on: 2019.2.1.0a6. 2019.1.0b5

Environment: Occurs only on mac

Stack Trace:

ArgumentException: The Assembly UnityEditor is referenced by UnityEditor.OSXStandalone.Extensions ('/Applications/Unity/Unity.app/Contents/PlaybackEngines/MacStandaloneSupport/UnityEditor.OSXStandalone.Extensions.dll'). But the dll is not allowed to be included or could not be found.
UnityEditor.AssemblyHelper.AddReferencedAssembliesRecurse (System.String assemblyPath, System.Collections.Generic.List`1[T] alreadyFoundAssemblies, System.String[] allAssemblyPaths, System.String[] foldersToSearch, System.Collections.Generic.Dictionary`2[TKey,TValue] cache, UnityEditor.BuildTarget target) (at /Users/builduser/buildslave/unity/build/Editor/Mono/AssemblyHelper.cs:154)
UnityEditor.AssemblyHelper.FindAssembliesReferencedBy (System.String[] paths, System.String[] foldersToSearch, UnityEditor.BuildTarget target) (at /Users/builduser/buildslave/unity/build/Editor/Mono/AssemblyHelper.cs:194)
UnityEngine.GUIUtility:ProcessEvent(Int32, IntPtr)