Add GN target for the sample shell

samples/samples.gyp

Index: samples/samples.gyp
diff --git a/samples/samples.gyp b/samples/samples.gyp
index 78a3ced8b1e87336dc44c75b4a6ec47ef419f8f0..c51250d7252f2ec7ce8f1155550b1c55fbfdc40e 100644
--- a/samples/samples.gyp
+++ b/samples/samples.gyp
@@ -29,6 +29,7 @@
   'variables': {
     'v8_code': 1,
     'v8_enable_i18n_support%': 1,
+    'v8_toolset_for_shell%': 'target',
   },
   'includes': ['../gypfiles/toolchain.gypi', '../gypfiles/features.gypi'],
   'target_defaults': {
@@ -60,6 +61,11 @@
       'sources': [
         'shell.cc',
       ],
+      'conditions': [
+        [ 'want_separate_host_toolset==1', {
+          'toolsets': [ '<(v8_toolset_for_shell)', ],
+        }],
+      ],
     },
     {
       'target_name': 'hello-world',