guard VisionOS for Unity 2021 compatibility

Author: amakropoulos

Runtime/LLMBuilder.cs

@@ -217,9 +217,11 @@ public static void BuildLibraryPlatforms(BuildTarget buildTarget)
                 case BuildTarget.iOS:
                     platforms.Add("ios-arm64");
                     break;
+#if UNITY_2022_3_OR_NEWER
                 case BuildTarget.VisionOS:
                     platforms.Add("visionos-arm64");
                     break;
+#endif
             }
 
             foreach (string source in Directory.GetDirectories(LLMUnitySetup.libraryPath))
@@ -256,7 +258,11 @@ public static void BuildLibraryPlatforms(BuildTarget buildTarget)
                 }
             }
 
-            if (buildTarget == BuildTarget.Android || buildTarget == BuildTarget.iOS || buildTarget == BuildTarget.VisionOS)
+            bool isVisionOS = false;
+#if UNITY_2022_3_OR_NEWER
+            isVisionOS = buildTarget == BuildTarget.VisionOS;
+#endif
+            if (buildTarget == BuildTarget.Android || buildTarget == BuildTarget.iOS || isVisionOS)
             {
                 foreach (string platform in platforms)
                 {
@@ -272,7 +278,11 @@ public static void BuildLibraryPlatforms(BuildTarget buildTarget)
 
         static void OnPostprocessAllAssets(string[] importedAssets, string[] deletedAssets, string[] movedAssets, string[] movedFromAssetPaths, bool didDomainReload)
         {
-            foreach (BuildTarget buildTarget in new BuildTarget[] { BuildTarget.iOS, BuildTarget.VisionOS, BuildTarget.Android })
+            List<BuildTarget> buildTargets = new List<BuildTarget>() { BuildTarget.iOS, BuildTarget.Android };
+#if UNITY_2022_3_OR_NEWER
+            buildTargets.Add(BuildTarget.VisionOS);
+#endif
+            foreach (BuildTarget buildTarget in buildTargets)
             {
                 string platformDir = Path.Combine("Assets", PluginDir(buildTarget.ToString(), true));
                 if (!Directory.Exists(platformDir)) continue;

Runtime/LLMUnitySetup.cs

@@ -230,7 +230,16 @@ public static string GetAssetPath(string relPath = "")
 
         public static string GetDownloadAssetPath(string relPath = "")
         {
-            string assetsDir = (Application.platform == RuntimePlatform.Android || Application.platform == RuntimePlatform.IPhonePlayer || Application.platform == RuntimePlatform.VisionOS) ? Application.persistentDataPath : Application.streamingAssetsPath;
+            string assetsDir = Application.streamingAssetsPath;
+
+            bool isVisionOS = false;
+#if UNITY_2022_3_OR_NEWER
+            isVisionOS = Application.platform == RuntimePlatform.VisionOS;
+#endif
+            if (Application.platform == RuntimePlatform.Android || Application.platform == RuntimePlatform.IPhonePlayer || isVisionOS)
+            {
+                assetsDir = Application.persistentDataPath;
+            }
             return Path.Combine(assetsDir, relPath).Replace('\\', '/');
         }