Add prop OSTailoredCode.IsWSL

src/BizHawk.Common/Extensions/StringExtensions.cs

@@ -5,6 +5,9 @@ namespace BizHawk.Common.StringExtensions
 {
 	public static class StringExtensions
 	{
+		public static bool Contains(this string haystack, string needle, StringComparison comparisonType)
+			=> haystack.IndexOf(needle, comparisonType) != -1;
+
 		/// <returns>
 		/// <see langword="true"/> if <paramref name="str"/> appears in <paramref name="options"/> (case-insensitive)
 		/// </returns>

src/BizHawk.Common/OSTailoredCode.cs

@@ -3,6 +3,8 @@ using System.Diagnostics;
 using System.Globalization;
 using System.Runtime.InteropServices;
 
+using BizHawk.Common.StringExtensions;
+
 #if EXE_PROJECT
 namespace EXE_PROJECT // Use a different namespace so the executable can still use this class' members without an implicit dependency on the BizHawk.Common library, and without resorting to code duplication.
 #else
@@ -44,10 +46,14 @@ namespace BizHawk.Common
 			return (winVer, null);
 		});
 
+		private static readonly Lazy<bool> _isWSL = new(() => IsUnixHost && SimpleSubshell("uname", "-r", "missing uname?").Contains("microsoft", StringComparison.InvariantCultureIgnoreCase));
+
 		public static (WindowsVersion Version, int? Win10Release)? HostWindowsVersion => _HostWindowsVersion.Value;
 
 		public static readonly bool IsUnixHost = CurrentOS != DistinctOS.Windows;
 
+		public static bool IsWSL => _isWSL.Value;
+
 		private static readonly Lazy<ILinkedLibManager> _LinkedLibManager = new Lazy<ILinkedLibManager>(() => CurrentOS switch
 		{
 			DistinctOS.Linux => new UnixMonoLLManager(),