When building standalone Dart executable, put implementation of dart:io natives in a separate libra…

runtime/bin/builtin_impl_sources.gypi

Index: runtime/bin/builtin_impl_sources.gypi
diff --git a/runtime/bin/builtin_impl_sources.gypi b/runtime/bin/builtin_impl_sources.gypi
index ad64eacf69edf8def5a67fb71f2f5f99bd6248d2..594a2d67d40d98555d0f83fb3d7f09b1e14041ed 100644
--- a/runtime/bin/builtin_impl_sources.gypi
+++ b/runtime/bin/builtin_impl_sources.gypi
@@ -2,8 +2,9 @@
 # for details. All rights reserved. Use of this source code is governed by a
 # BSD-style license that can be found in the LICENSE file.
 
-# This file contains all C++ sources for the dart:builtin and dart:io
-# libraries.
+# This file contains all C++ sources for the dart:builtin library and
+# some of the C++ sources for the dart:io library.  The rest are in
+# io_impl_sources.gypi.
 {
   'sources': [
     'io_buffer.cc',
@@ -33,15 +34,6 @@
     'directory_linux.cc',
     'directory_macos.cc',
     'directory_win.cc',
-    'eventhandler.cc',
-    'eventhandler.h',
-    'eventhandler_android.cc',
-    'eventhandler_linux.cc',
-    'eventhandler_linux.h',
-    'eventhandler_macos.cc',
-    'eventhandler_macos.h',
-    'eventhandler_win.cc',
-    'eventhandler_win.h',
     'extensions.h',
     'extensions.cc',
     'extensions_android.cc',
@@ -67,18 +59,6 @@
     'platform_linux.cc',
     'platform_macos.cc',
     'platform_win.cc',
-    'process.cc',
-    'process.h',
-    'process_android.cc',
-    'process_linux.cc',
-    'process_macos.cc',
-    'process_win.cc',
-    'socket.cc',
-    'socket.h',
-    'socket_android.cc',
-    'socket_linux.cc',
-    'socket_macos.cc',
-    'socket_win.cc',
     'set.h',
     'set_test.cc',
     'thread.h',