Stop passing removed parameter to create_snapshot_bin.py to fix GYP/Dartium build.

runtime/bin/bin.gypi

 # Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 # 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.
 
 {
   'variables': {
     'gen_source_dir': '<(SHARED_INTERMEDIATE_DIR)',
 
     'io_cc_file': '<(gen_source_dir)/io_gen.cc',
     'io_patch_cc_file': '<(gen_source_dir)/io_patch_gen.cc',
@@ skipping 989 matching lines @@
             '<(gen_snapshot_stamp_file)',
           ],
           'action': [
             'python',
             'tools/create_snapshot_bin.py',
             '--executable',
             '<(PRODUCT_DIR)/<(EXECUTABLE_PREFIX)gen_snapshot<(EXECUTABLE_SUFFIX)',
             '--snapshot_kind', 'core',
             '--vm_output_bin', '<(vm_isolate_snapshot_bin_file)',
             '--isolate_output_bin', '<(isolate_snapshot_bin_file)',
-            '--target_os', '<(OS)',
             '--timestamp_file', '<(gen_snapshot_stamp_file)',
           ],
           'message': 'Generating ''<(vm_isolate_snapshot_bin_file)'' ''<(isolate_snapshot_bin_file)'' files.'
         },
       ],
     },
     {
       # Generate snapshot file.
       'target_name': 'generate_snapshot_file',
       'type': 'none',
@@ skipping 413 matching lines @@
         }],
         ['OS=="linux"', {
           'cflags': [
             '-fPIC',
           ],
         }],
       ],
     },
   ],
 }