Reproduction steps:

1. Create a New Project
2. Import Unity IAP
3. Switch to "IL2CPP" Scripting Backend
4. Build for MacOS

Expected Result: Build Succeeds
Actual Result: Build Fails

Reproduced with: 2019.2.0a4, 2019.1.0b4, 2018.3.7f1, 2018.1.9f2
Did not reproduce on: 2018.1.0a5, 2017.4.20f2

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Still occurs On 2019.3.0b7, 2020.1.0a9

Occurs on 2019.2.0b7 even after removing the IAP packages.

1. Stack Trace1: ailed running /Applications/Unity 2019.1.0b6/Unity.app/Contents/il2cpp/build/il2cppcore/il2cppcore.dll --convert-to-cpp --emit-null-checks --enable-array-bounds-check --dotnetprofile="unityaot" --compile-cpp --libil2cpp-static --platform="MacOSX" --architecture="x64" --configuration="Release" --outputpath="/Users/macmini6/Downloads/New Unity Project (70)/Temp/StagingArea/Data/Native/GameAssembly.dylib" --cachedirectory="/Users/macmini6/Downloads/New Unity Project (70)/Assets/../Library/il2cpp_cache" --profiler-report --map-file-parser="/Applications/Unity 2019.1.0b6/Unity.app/Contents/Tools/MapFileParser/MapFileParser" --directory="/Users/macmini6/Downloads/New Unity Project (70)/Temp/StagingArea/Data/Managed" --generatedcppdir="/Users/macmini6/Downloads/New Unity Project (70)/Temp/StagingArea/Data/il2cppOutput"

stdout:
il2cpp.exe didn't catch exception: System.TypeInitializationException: The type initializer for 'Unity.IL2CPP.Building.ToolChains.XcodeInstallation' threw an exception. ---> System.ArgumentNullException: Value cannot be null.
at NiceIO.NPath..ctor(String path)
at NiceIO.NPath.op_Implicit(String input)
at Unity.IL2CPP.Building.ToolChains.XcodeInstallation..cctor()
--- End of inner exception stack trace ---
at Unity.IL2CPP.Building.ToolChains.ClangToolChain.CanBuildInCurrentEnvironment()
at Unity.IL2CPP.Building.CppProgramBuilder.ThrowIfCannotBuildInCurrentEnvironment()
at Unity.IL2CPP.Building.CppProgramBuilder.Build(IBuildStatistics& statistics)
at il2cpp.Program.DoRun(String[] args)
at il2cpp.Program.Run(String[] args)
at il2cpp.Program.Main(String[] args)
stderr:
xcrun: error: invalid active developer path (/Library/Developer/CommandLineTools), missing xcrun at: /Library/Developer/CommandLineTools/usr/bin/xcrun
xcrun: error: invalid active developer path (/Library/Developer/CommandLineTools), missing xcrun at: /Library/Developer/CommandLineTools/usr/bin/xcrun

Unhandled Exception: System.TypeInitializationException: The type initializer for 'Unity.IL2CPP.Building.ToolChains.XcodeInstallation' threw an exception. ---> System.ArgumentNullException: Value cannot be null.
at NiceIO.NPath..ctor(String path)
at NiceIO.NPath.op_Implicit(String input)
at Unity.IL2CPP.Building.ToolChains.XcodeInstallation..cctor()
--- End of inner exception stack trace ---
at Unity.IL2CPP.Building.ToolChains.ClangToolChain.CanBuildInCurrentEnvironment()
at Unity.IL2CPP.Building.CppProgramBuilder.ThrowIfCannotBuildInCurrentEnvironment()
at Unity.IL2CPP.Building.CppProgramBuilder.Build(IBuildStatistics& statistics)
at il2cpp.Program.DoRun(String[] args)
at il2cpp.Program.Run(String[] args)
at il2cpp.Program.Main(String[] args)
at Program.Main(String[] args)

UnityEngine.Debug:LogError(Object)
UnityEditorInternal.Runner:RunProgram(Program, String, String, String, CompilerOutputParserBase) (at /Users/builduser/buildslave/unity/build/Editor/Mono/BuildPipeline/BuildUtils.cs:128)
UnityEditorInternal.Runner:RunNetCoreProgram(String, String, String, CompilerOutputParserBase, Action`1) (at /Users/builduser/buildslave/unity/build/Editor/Mono/BuildPipeline/BuildUtils.cs:79)
UnityEditorInternal.IL2CPPBuilder:RunIl2CppWithArguments(List`1, Action`1, String) (at /Users/builduser/buildslave/unity/build/Editor/Mono/BuildPipeline/Il2Cpp/IL2CPPUtils.cs:486)
UnityEditorInternal.IL2CPPBuilder:ConvertPlayerDlltoCpp(String, String, String, Boolean) (at /Users/builduser/buildslave/unity/build/Editor/Mono/BuildPipeline/Il2Cpp/IL2CPPUtils.cs:469)
UnityEditorInternal.IL2CPPBuilder:Run() (at /Users/builduser/buildslave/unity/build/Editor/Mono/BuildPipeline/Il2Cpp/IL2CPPUtils.cs:327)
UnityEditorInternal.IL2CPPUtils:RunIl2Cpp(String, IIl2CppPlatformProvider, Action`1, RuntimeClassRegistry) (at /Users/builduser/buildslave/unity/build/Editor/Mono/BuildPipeline/Il2Cpp/IL2CPPUtils.cs:70)
DesktopStandalonePostProcessor:SetupStagingArea(BuildPostProcessArgs, HashSet`1) (at /Users/builduser/buildslave/unity/build/Editor/Mono/BuildPipeline/DesktopStandalonePostProcessor.cs:245)
DesktopStandalonePostProcessor:PostProcess(BuildPostProcessArgs) (at /Users/builduser/buildslave/unity/build/Editor/Mono/BuildPipeline/DesktopStandalonePostProcessor.cs:46)
UnityEngine.GUIUtility:ProcessEvent(Int32, IntPtr)

2. Stack Trace 2: Exception: /Applications/Unity/Unity.app/Contents/il2cpp/build/il2cppcore/il2cppcore.dll did not run properly!
UnityEditorInternal.Runner.RunProgram (UnityEditor.Utils.Program p, System.String exe, System.String args, System.String workingDirectory, UnityEditor.Scripting.Compilers.CompilerOutputParserBase parser) (at /Users/builduser/buildslave/unity/build/Editor/Mono/BuildPipeline/BuildUtils.cs:130)
UnityEditorInternal.Runner.RunNetCoreProgram (System.String exe, System.String args, System.String workingDirectory, UnityEditor.Scripting.Compilers.CompilerOutputParserBase parser, System.Action`1[T] setupStartInfo) (at /Users/builduser/buildslave/unity/build/Editor/Mono/BuildPipeline/BuildUtils.cs:79)
UnityEditorInternal.IL2CPPBuilder.RunIl2CppWithArguments (System.Collections.Generic.List`1[T] arguments, System.Action`1[T] setupStartInfo, System.String workingDirectory) (at /Users/builduser/buildslave/unity/build/Editor/Mono/BuildPipeline/Il2Cpp/IL2CPPUtils.cs:494)
UnityEditorInternal.IL2CPPBuilder.ConvertPlayerDlltoCpp (System.String inputDirectory, System.String outputDirectory, System.String workingDirectory, System.Boolean platformSupportsManagedDebugging) (at /Users/builduser/buildslave/unity/build/Editor/Mono/BuildPipeline/Il2Cpp/IL2CPPUtils.cs:477)
UnityEditorInternal.IL2CPPBuilder.Run () (at /Users/builduser/buildslave/unity/build/Editor/Mono/BuildPipeline/Il2Cpp/IL2CPPUtils.cs:334)
UnityEditorInternal.IL2CPPUtils.RunIl2Cpp (System.String stagingAreaData, UnityEditorInternal.IIl2CppPlatformProvider platformProvider, System.Action`1[T] modifyOutputBeforeCompile, UnityEditor.RuntimeClassRegistry runtimeClassRegistry) (at /Users/builduser/buildslave/unity/build/Editor/Mono/BuildPipeline/Il2Cpp/IL2CPPUtils.cs:70)
DesktopStandalonePostProcessor.SetupStagingArea (UnityEditor.Modules.BuildPostProcessArgs args, System.Collections.Generic.HashSet`1[T] filesToNotOverwrite) (at /Users/builduser/buildslave/unity/build/Editor/Mono/BuildPipeline/DesktopStandalonePostProcessor.cs:245)
DesktopStandalonePostProcessor.PostProcess (UnityEditor.Modules.BuildPostProcessArgs args) (at /Users/builduser/buildslave/unity/build/Editor/Mono/BuildPipeline/DesktopStandalonePostProcessor.cs:46)
Rethrow as BuildFailedException: Exception of type 'UnityEditor.Build.BuildFailedException' was thrown.
DesktopStandalonePostProcessor.PostProcess (UnityEditor.Modules.BuildPostProcessArgs args) (at /Users/builduser/buildslave/unity/build/Editor/Mono/BuildPipeline/DesktopStandalonePostProcessor.cs:61)
UnityEditor.OSXStandalone.OSXDesktopStandalonePostProcessor.PostProcess (UnityEditor.Modules.BuildPostProcessArgs args) (at /Users/builduser/buildslave/unity/build/PlatformDependent/OSXPlayer/Extensions/Managed/OSXDesktopStandalonePostProcessor.cs:248)
UnityEditor.Modules.DefaultBuildPostprocessor.PostProcess (UnityEditor.Modules.BuildPostProcessArgs args, UnityEditor.BuildProperties& outProperties) (at /Users/builduser/buildslave/unity/build/Editor/Mono/Modules/DefaultBuildPostprocessor.cs:27)
UnityEditor.PostprocessBuildPlayer.Postprocess (UnityEditor.BuildTargetGroup targetGroup, UnityEditor.BuildTarget target, System.String installPath, System.String companyName, System.String productName, System.Int32 width, System.Int32 height, UnityEditor.BuildOptions options, UnityEditor.RuntimeClassRegistry usedClassRegistry, UnityEditor.Build.Reporting.BuildReport report) (at /Users/builduser/buildslave/unity/build/Editor/Mono/BuildPipeline/PostprocessBuildPlayer.cs:281)
UnityEngine.GUIUtility:ProcessEvent(Int32, IntPtr)

Note:
IL2CPP for mac only implemented from 2018.1.0a6