Make msvcrt Windows-only (#1708)

Author: BCSharp

Src/IronPython.Modules/msvcrt.cs

@@ -11,6 +11,7 @@
 using System.Numerics;
 using System.Reflection;
 using System.Runtime.InteropServices;
+using System.Runtime.Versioning;
 
 using Microsoft.Scripting.Runtime;
 
@@ -24,6 +25,7 @@
 [assembly: PythonModule("msvcrt", typeof(IronPython.Modules.PythonMsvcrt), PlatformsAttribute.PlatformFamily.Windows)]
 namespace IronPython.Modules {
     [PythonType("msvcrt")]
+    [SupportedOSPlatform("windows")]
     public class PythonMsvcrt {
         public const string __doc__ = "Functions from the Microsoft Visual C Runtime.";
 
@@ -76,10 +78,6 @@ private static bool TryGetFileHandle(Stream stream, out object handle) {
                 handle = ((PipeStream)stream).SafePipeHandle.DangerousGetHandle().ToPython();
                 return true;
             }
-            if (RuntimeInformation.IsOSPlatform(OSPlatform.Linux) || RuntimeInformation.IsOSPlatform(OSPlatform.OSX)) {
-                handle = GetFileHandleUnix();
-                if (handle != null) return true;
-            }
 #endif
 
             // if all else fails try reflection
@@ -91,14 +89,6 @@ private static bool TryGetFileHandle(Stream stream, out object handle) {
 
             handle = null;
             return false;
-
-            // Isolate Mono.Unix from the rest of the method so that we don't try to load the Mono.Unix assembly on Windows.
-            object GetFileHandleUnix() {
-                if (stream is Mono.Unix.UnixStream) {
-                    return ((Mono.Unix.UnixStream)stream).Handle;
-                }
-                return null;
-            }
         }
 
         [Documentation(@"get_osfhandle(fd) -> file handle