Remove some warnings and cleaning code (#1736)

Ryujinx.Common/SystemInfo/MacOSSysteminfo.cs

@@ -1,11 +1,13 @@
 using System;
 using System.Runtime.CompilerServices;
 using System.Runtime.InteropServices;
+using System.Runtime.Versioning;
 using System.Text;
 using Ryujinx.Common.Logging;
 
 namespace Ryujinx.Common.SystemInfo
 {
+    [SupportedOSPlatform("macos")]
     internal class MacOSSysteminfo : SystemInfo
     {
         public override string CpuName { get; }