Do not remote duplicate entries from ldflags when generating ninja files as it changes behavior

test/ninja/duplicate-ldflags/test.gyp

 # Copyright (c) 2014 Google Inc. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 {
   'targets': [
     {
-      'target_name': 'f',
+      'target_name': 'All',
       'type': 'executable',
+      'ldflags': [
+        '-Wl,--whole-archive lib1.a',
+        '-Wl,--no-whole-archive',
+
+        '-Wl,--whole-archive lib2.a',
+        '-Wl,--no-whole-archive',
+      ],
       'sources': [
-        'f.c',
-      ],
-    },
-    {
-      'target_name': 'g',
-      'type': 'executable',
-      'sources': [
-        'g.c',
-      ],
-      'dependencies': [
-        'f',
+        'main.cc',
       ],
     },
   ],
 }