Add API for runtime CoreCLR check (#912)

Add API for runtime CoreCLR check

Author: rjmholt

src/PowerShellEditorServices/Utility/Utils.cs

@@ -0,0 +1,22 @@
+//
+// Copyright (c) Microsoft. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+//
+
+namespace Microsoft.PowerShell.EditorServices
+{
+    /// <summary>
+    /// General purpose common utilities to prevent reimplementation.
+    /// </summary>
+    internal static class Utils
+    {
+        /// <summary>
+        /// True if we are running on .NET Core, false otherwise.
+        /// </summary>
+#if CoreCLR
+        public static bool IsNetCore { get; } = true;
+#else
+        public static bool IsNetCore { get; } = false;
+#endif
+    }
+}