Add EnvironmentAugments to corert

src/System.Private.CoreLib/src/Internal/Runtime/Augments/EnvironmentAugments.cs

@@ -0,0 +1,21 @@
+// 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 Internal.Runtime.Augments
+{
+    /// <summary>For internal use only.  Exposes runtime functionality to the Environments implementation in corefx.</summary>
+    public static class EnvironmentAugments
+    {
+        public static int CurrentManagedThreadId => Environment.CurrentManagedThreadId;
+        public static void Exit(int exitCode) => Environment.Exit(exitCode);
+        public static int ExitCode { get { return 0; } set { throw new PlatformNotSupportedException(); } }
+        public static void FailFast(string message, Exception error) => Environment.FailFast(message, error);
+        public static string[] GetCommandLineArgs() => Environment.GetCommandLineArgs();
+        public static bool HasShutdownStarted => Environment.HasShutdownStarted;
+        public static string StackTrace => Environment.StackTrace;
+        public static int TickCount => Environment.TickCount;
+    }
+}

src/System.Private.CoreLib/src/System.Private.CoreLib.csproj

@@ -86,6 +86,7 @@
     <Compile Include="Internal\Runtime\Augments\DesktopSupportCallbacks.cs" />
     <Compile Include="Internal\Runtime\Augments\DynamicDelegateAugments.cs" />
     <Compile Include="Internal\Runtime\Augments\EnumInfo.cs" />
+    <Compile Include="Internal\Runtime\Augments\EnvironmentAugments.cs" />
   </ItemGroup>
 
   <ItemGroup Condition="'$(IsProjectNLibrary)' == 'true'">

src/System.Private.CoreLib/src/System/Environment.cs

@@ -105,7 +105,6 @@ public static String NewLine
             }
         }
 
-#if CORERT
         private static string[] s_commandLineArgs;
 
         internal static void SetCommandLineArgs(string[] args)
@@ -115,9 +114,8 @@ internal static void SetCommandLineArgs(string[] args)
 
         public static string[] GetCommandLineArgs()
         {
-            return (string[])s_commandLineArgs.Clone();
+            return (string[])s_commandLineArgs?.Clone();
         }
-#endif
 
         public static String StackTrace
         {