Disable warnings in copypasta'd code

fixes 160217ef7

src/BizHawk.Common/Extensions/Pillaged/PathInternal.Unix.cs

@@ -1,6 +1,8 @@
 // Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 
+#pragma warning disable
+
 using System;
 using System.Diagnostics;
 using System.Text;

src/BizHawk.Common/Extensions/Pillaged/PathInternal.Windows.cs

@@ -1,7 +1,8 @@
 // Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 
-#nullable enable
+#pragma warning disable
+
 using System.Diagnostics.CodeAnalysis;
 using System.Runtime.CompilerServices;