iOS not running in Xcode (Architecture issue)

Found a thread that said for this issue to change:
1) Scripting Backend from Mono to IL2CPP
and
2) Architecture to Universal

I did this but there's a Build Failure. Can anybody help?
(BTW, I tried keeping it Mono and changing it in Xcode to Standard Architectures, but that didn't work either (looks like linker issues).

--------
Failed running /Applications/Unity/Unity.app/Contents/il2cpp/build/UnityLinker.exe --api=NET_2_0_Subset -out="/Users/math/projects/RT/Temp/StagingArea/Data/Managed/tempStrip" -l=none -c=link --link-symbols -x="/Applications/Unity/PlaybackEngines/iOSSupport/Whitelists/Core.xml" -f="/Applications/Unity/Unity.app/Contents/il2cpp/LinkerDescriptors" -x "/Users/math/projects/RT/Temp/StagingArea/Data/Managed/../platform_native_link.xml" -x "/Users/math/projects/RT/Temp/StagingArea/Data/methods_pointedto_by_uievents.xml" -x "/Users/math/projects/RT/Temp/StagingArea/Data/UnityEngine.xml" -x "/Users/math/projects/RT/Temp/StagingArea/Data/preserved_derived_types.xml" -x "/Users/math/projects/RT/Assets/link.xml" -d "/Users/math/projects/RT/Temp/StagingArea/Data/Managed" -a "/Users/math/projects/RT/Temp/StagingArea/Data/Managed/Assembly-CSharp.dll" -a "/Users/math/projects/RT/Temp/StagingArea/Data/Managed/Assembly-UnityScript.dll" -a "/Users/math/projects/RT/Temp/StagingArea/Data/Managed/UnityEngine.UI.dll"

stdout:
Fatal error in Unity CIL Linker
System.ArgumentException: Unable to find the file for the assembly named 'U3DXTCore, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null' specified in link file '/Users/math/projects/RT/Assets/link.xml'. Should this assembly be in the project? Use the 'ignoreIfMissing="1"' attribute if this assembly may not always exist. ---> Mono.Cecil.AssemblyResolutionException: Failed to resolve assembly: 'U3DXTCore, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null'
at Mono.Linker.LinkContext.Resolve (Mono.Cecil.IMetadataScope scope) [0x00047] in <09bca01fd71241c7a07af8c71eb6ae1a>:0
at UnityLinker.Steps.UnityResolveFromXmlStep.GetAssembly (Mono.Linker.LinkContext context, Mono.Cecil.AssemblyNameReference assemblyName) [0x00001] in <81b71c29c35449f8a666455c78a2dcfb>:0
at UnityLinker.Steps.UnityResolveFromXmlStep.ProcessAssemblies (Mono.Linker.LinkContext context, System.Xml.XPath.XPathNodeIterator iterator) [0x00014] in <81b71c29c35449f8a666455c78a2dcfb>:0
--- End of inner exception stack trace ---
at UnityLinker.Steps.UnityResolveFromXmlStep.ProcessAssemblies (Mono.Linker.LinkContext context, System.Xml.XPath.XPathNodeIterator iterator) [0x00104] in <81b71c29c35449f8a666455c78a2dcfb>:0
at UnityLinker.Steps.UnityResolveFromXmlStep.Process () [0x0002b] in <81b71c29c35449f8a666455c78a2dcfb>:0
at Mono.Linker.Steps.BaseStep.Process (Mono.Linker.LinkContext context) [0x00018] in <09bca01fd71241c7a07af8c71eb6ae1a>:0
at Mono.Linker.Pipeline.Process (Mono.Linker.LinkContext context) [0x00020] in <09bca01fd71241c7a07af8c71eb6ae1a>:0
at UnityLinker.UnityDriver.Run () [0x00086] in <81b71c29c35449f8a666455c78a2dcfb>:0
at UnityLinker.UnityDriver.RunDriverWithoutErrorHandling () [0x00001] in <81b71c29c35449f8a666455c78a2dcfb>:0
at UnityLinker.UnityDriver.RunDriver () [0x00002] in <81b71c29c35449f8a666455c78a2dcfb>:0
stderr:

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:RunManagedProgram(String, String, String, CompilerOutputParserBase, Action`1) (at /Users/builduser/buildslave/unity/build/Editor/Mono/BuildPipeline/BuildUtils.cs:73)
UnityEditorInternal.AssemblyStripper:RunAssemblyLinker(IEnumerable`1, String&, String&, String, String) (at /Users/builduser/buildslave/unity/build/Editor/Mono/BuildPipeline/AssemblyStripper.cs:89)
UnityEditorInternal.AssemblyStripper:StripAssembliesTo(String[], String[], String, String, String&, String&, String, IIl2CppPlatformProvider, IEnumerable`1) (at /Users/builduser/buildslave/unity/build/Editor/Mono/BuildPipeline/AssemblyStripper.cs:82)
UnityEditorInternal.AssemblyStripper:RunAssemblyStripper(String, IEnumerable, String, String[], String[], String, IIl2CppPlatformProvider, RuntimeClassRegistry) (at /Users/builduser/buildslave/unity/build/Editor/Mono/BuildPipeline/AssemblyStripper.cs:204)
UnityEditorInternal.AssemblyStripper:StripAssemblies(String, IIl2CppPlatformProvider, RuntimeClassRegistry) (at /Users/builduser/buildslave/unity/build/Editor/Mono/BuildPipeline/AssemblyStripper.cs:114)
UnityEditorInternal.IL2CPPBuilder:Run() (at /Users/builduser/buildslave/unity/build/Editor/Mono/BuildPipeline/Il2Cpp/IL2CPPUtils.cs:143)
UnityEditorInternal.IL2CPPUtils:RunIl2Cpp(String, String, IIl2CppPlatformProvider, Action`1, RuntimeClassRegistry, Boolean) (at /Users/builduser/buildslave/unity/build/Editor/Mono/BuildPipeline/Il2Cpp/IL2CPPUtils.cs:34)
UnityEngine.GUIUtilityrocessEvent(Int32, IntPtr)

Exception: /Applications/Unity/Unity.app/Contents/il2cpp/build/UnityLinker.exe 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.RunManagedProgram (System.String exe, System.String args, System.String workingDirectory, UnityEditor.Scripting.Compilers.CompilerOutputParserBase parser, System.Action`1 setupStartInfo) (at /Users/builduser/buildslave/unity/build/Editor/Mono/BuildPipeline/BuildUtils.cs:73)
UnityEditorInternal.AssemblyStripper.RunAssemblyLinker (IEnumerable`1 args, System.String& out, System.String& err, System.String linkerPath, System.String workingDirectory) (at /Users/builduser/buildslave/unity/build/Editor/Mono/BuildPipeline/AssemblyStripper.cs:89)
UnityEditorInternal.AssemblyStripper.StripAssembliesTo (System.String[] assemblies, System.String[] searchDirs, System.String outputFolder, System.String workingDirectory, System.String& output, System.String& error, System.String linkerPath, IIl2CppPlatformProvider platformProvider, IEnumerable`1 additionalBlacklist) (at /Users/builduser/buildslave/unity/build/Editor/Mono/BuildPipeline/AssemblyStripper.cs:82)
UnityEditorInternal.AssemblyStripper.RunAssemblyStripper (System.String stagingAreaData, IEnumerable assemblies, System.String managedAssemblyFolderPath, System.String[] assembliesToStrip, System.String[] searchDirs, System.String monoLinkerPath, IIl2CppPlatformProvider platformProvider, UnityEditor.RuntimeClassRegistry rcr) (at /Users/builduser/buildslave/unity/build/Editor/Mono/BuildPipeline/AssemblyStripper.cs:204)
UnityEditorInternal.AssemblyStripper.StripAssemblies (System.String stagingAreaData, IIl2CppPlatformProvider platformProvider, UnityEditor.RuntimeClassRegistry rcr) (at /Users/builduser/buildslave/unity/build/Editor/Mono/BuildPipeline/AssemblyStripper.cs:114)
UnityEditorInternal.IL2CPPBuilder.Run () (at /Users/builduser/buildslave/unity/build/Editor/Mono/BuildPipeline/Il2Cpp/IL2CPPUtils.cs:143)
UnityEditorInternal.IL2CPPUtils.RunIl2Cpp (System.String tempFolder, System.String stagingAreaData, IIl2CppPlatformProvider platformProvider, System.Action`1 modifyOutputBeforeCompile, UnityEditor.RuntimeClassRegistry runtimeClassRegistry, Boolean debugBuild) (at /Users/builduser/buildslave/unity/build/Editor/Mono/BuildPipeline/Il2Cpp/IL2CPPUtils.cs:34)
UnityEditor.iOS.PostProcessiPhonePlayer.CrossCompileManagedDlls (BuildSettings bs, UnityEditor.iOS.ProjectPaths paths, UnityEditor.AssemblyReferenceChecker checker, UnityEditor.RuntimeClassRegistry usedClassRegistry, UnityEditor.BuildReporting.BuildReport buildReport) (at /Users/builduser/buildslave/unity/build/PlatformDependent/iPhonePlayer/Extensions/Common/BuildPostProcessor.cs:741)
UnityEditor.iOS.PostProcessiPhonePlayer.PostProcess (BuildSettings bs, UnityEditor.iOS.ProjectPaths paths, UnityEditor.RuntimeClassRegistry usedClassRegistry, UnityEditor.BuildReporting.BuildReport buildReport) (at /Users/builduser/buildslave/unity/build/PlatformDependent/iPhonePlayer/Extensions/Common/BuildPostProcessor.cs:594)
UnityEditor.iOS.PostProcessiPhonePlayer.PostProcess (PostProcessorSettings postProcessorSettings, BuildPostProcessArgs args) (at /Users/builduser/buildslave/unity/build/PlatformDependent/iPhonePlayer/Extensions/Common/BuildPostProcessor.cs:555)
UnityEditor.iOS.iOSBuildPostprocessor.PostProcess (BuildPostProcessArgs args) (at /Users/builduser/buildslave/unity/build/PlatformDependent/iPhonePlayer/Extensions/Common/ExtensionModule.cs:37)
UnityEditor.PostprocessBuildPlayer.Postprocess (BuildTargetGroup targetGroup, BuildTarget target, System.String installPath, System.String companyName, System.String productName, Int32 width, Int32 height, BuildOptions options, UnityEditor.RuntimeClassRegistry usedClassRegistry, UnityEditor.BuildReporting.BuildReport report) (at /Users/builduser/buildslave/unity/build/Editor/Mono/BuildPipeline/PostprocessBuildPlayer.cs:271)
UnityEngine.GUIUtilityrocessEvent(Int32, IntPtr)

Build completed with a result of 'Failed'
UnityEngine.GUIUtilityrocessEvent(Int32, IntPtr)

UnityEditor.BuildPlayerWindow+BuildMethodException: 4 errors
at UnityEditor.BuildPlayerWindow+DefaultBuildMethods.BuildPlayer (BuildPlayerOptions options) [0x00207] in /Users/builduser/buildslave/unity/build/Editor/Mono/BuildPlayerWindowBuildMethods.cs:172
at UnityEditor.BuildPlayerWindow.CallBuildMethods (Boolean askForBuildLocation, BuildOptions defaultBuildOptions) [0x00050] in /Users/builduser/buildslave/unity/build/Editor/Mono/BuildPlayerWindowBuildMethods.cs:83
UnityEngine.GUIUtilityrocessEvent(Int32, IntPtr)

 

Thanks Aurimas-Cernius. Couldn't find that specific one, but I deleted some JSON stuff I wasn't using that was in the Resource Folder. ..maybe that was including something like that. Seems to work now.