use proper os comparison

Jellyfin.Api/Helpers/ProgressiveFileCopier.cs

@@ -1,5 +1,7 @@
 using System;
+using System.Buffers;
 using System.IO;
+using System.Runtime.InteropServices;
 using System.Threading;
 using System.Threading.Tasks;
 using Jellyfin.Api.Models.PlaybackDtos;
@@ -82,7 +84,7 @@ namespace Jellyfin.Api.Helpers
                 var allowAsyncFileRead = false;
 
                 // use non-async filestream along with read due to https://github.com/dotnet/corefx/issues/6039
-                if (Environment.OSVersion.Platform != PlatformID.Win32NT)
+                if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows))
                 {
                     fileOptions |= FileOptions.Asynchronous;
                     allowAsyncFileRead = true;