Naricc/test mono is mono (#36079)

Add test to test if we are running mono.

src/coreclr/tests/issues.targets

@@ -116,6 +116,9 @@
         <ExcludeList Include="$(XunitTestBinBase)/Loader/classloader/generics/Variance/Interfaces/Interfaces001/*">
             <Issue>https://github.com/dotnet/runtime/issues/3893</Issue>
         </ExcludeList>
+	<ExcludeList Include="$(XunitTestBinBase)/baseservices/mono/runningmono/*">
+            <Issue>This test is to verify we are running mono, and therefore only makes sense on mono.</Issue>
+	</ExcludeList>
     </ItemGroup>
 
     <!-- All Unix targets on all runtimes -->

src/coreclr/tests/src/baseservices/mono/runningmono.cs

@@ -0,0 +1,26 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+using System;
+
+namespace TestRunningMono
+{
+    class Program
+    {
+        public static int Main(string[] args)
+        {
+             const int Pass = 100, Fail = 1;
+             bool isMono = typeof(object).Assembly.GetType("Mono.RuntimeStructs") != null;
+
+             if(isMono)
+             {
+                 return Pass;
+             }
+             else
+             {
+                 return Fail;
+             }
+        }
+   }
+}
+

src/coreclr/tests/src/baseservices/mono/runningmono.csproj

@@ -0,0 +1,11 @@
+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <Optimize>false</Optimize>
+    <CLRTestPriority>0</CLRTestPriority>
+  </PropertyGroup>
+  <ItemGroup>
+    <Compile Include="runningmono.cs" />
+  </ItemGroup>
+</Project>
+