Add menu item for adding/removing asset importer define

Author: keveleigh

Assets/MRTK/Core/Utilities/Gltf/Serialization/Importers/GltfEditorImporter.cs

@@ -1,6 +1,7 @@
 // Copyright (c) Microsoft Corporation.
 // Licensed under the MIT License.
 
+using Microsoft.MixedReality.Toolkit.Utilities.Editor;
 using Microsoft.MixedReality.Toolkit.Utilities.Gltf.Schema;
 using System.IO;
 using UnityEditor;
@@ -16,6 +17,22 @@ namespace Microsoft.MixedReality.Toolkit.Utilities.Gltf.Serialization.Editor
 {
     public static class GltfEditorImporter
     {
+#if MRTK_GLTF_IMPORTER_OFF
+        [MenuItem("Mixed Reality/Toolkit/Utilities/Enable MRTK glTF asset importer")]
+#else
+        [MenuItem("Mixed Reality/Toolkit/Utilities/Disable MRTK glTF asset importer")]
+#endif
+        private static void ReconcileGltfImporterDefine()
+        {
+            BuildTargetGroup group = BuildPipeline.GetBuildTargetGroup(EditorUserBuildSettings.activeBuildTarget);
+
+#if MRTK_GLTF_IMPORTER_OFF
+            ScriptUtilities.RemoveScriptingDefinitions(group, "MRTK_GLTF_IMPORTER_OFF");
+#else
+            ScriptUtilities.AppendScriptingDefinitions(group, "MRTK_GLTF_IMPORTER_OFF");
+#endif
+        }
+
         public static async void OnImportGltfAsset(AssetImportContext context)
         {
             var importedObject = await GltfUtility.ImportGltfObjectFromPathAsync(context.assetPath);