Gate the macOS only functions

MediaBrowser.MediaEncoding/Encoder/ApplePlatformHelper.cs

@@ -3,6 +3,7 @@
 using System;
 using System.Linq;
 using System.Runtime.InteropServices;
+using System.Runtime.Versioning;
 using Microsoft.Extensions.Logging;
 
 namespace MediaBrowser.MediaEncoding.Encoder;
@@ -10,6 +11,7 @@ namespace MediaBrowser.MediaEncoding.Encoder;
 /// <summary>
 /// Helper class for Apple platform specific operations.
 /// </summary>
+[SupportedOSPlatform("macos")]
 public static class ApplePlatformHelper
 {
     private static readonly string[] _av1DecodeBlacklistedCpuClass = ["M1", "M2"];

MediaBrowser.MediaEncoding/Encoder/EncoderValidator.cs

@@ -5,6 +5,7 @@ using System.Collections.Generic;
 using System.Diagnostics;
 using System.Globalization;
 using System.Linq;
+using System.Runtime.Versioning;
 using System.Text.RegularExpressions;
 using Microsoft.Extensions.Logging;
 
@@ -437,6 +438,7 @@ namespace MediaBrowser.MediaEncoding.Encoder
             }
         }
 
+        [SupportedOSPlatform("macos")]
         public bool CheckIsVideoToolboxAv1DecodeAvailable()
         {
             return ApplePlatformHelper.HasAv1HardwareAccel(_logger);