Add missing line to gyp file.

runtime/vm/vm.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)',
     'libgen_in_cc_file': '../lib/libgen_in.cc',
     'builtin_in_cc_file': '../bin/builtin_in.cc',
     'async_cc_file': '<(gen_source_dir)/async_gen.cc',
@@ skipping 96 matching lines @@
         'generate_convert_cc_file#host',
         'generate_convert_patch_cc_file#host',
         'generate_math_cc_file#host',
         'generate_math_patch_cc_file#host',
         'generate_isolate_cc_file#host',
         'generate_isolate_patch_cc_file#host',
         'generate_json_cc_file#host',
         'generate_mirrors_cc_file#host',
         'generate_mirrors_patch_cc_file#host',
         'generate_platform_cc_file#host',
+        'generate_platform_patch_cc_file#host',
         'generate_typed_data_cc_file#host',
         'generate_typed_data_patch_cc_file#host',
         'generate_utf_cc_file#host',
       ],
       'includes': [
         '../lib/async_sources.gypi',
         '../lib/collection_sources.gypi',
         '../lib/corelib_sources.gypi',
         '../lib/isolate_sources.gypi',
         '../lib/math_sources.gypi',
@@ skipping 939 matching lines @@
             '--include', 'INTENTIONALLY_LEFT_BLANK',
             '--var_name', 'INTENTIONALLY_LEFT_BLANK_TOO',
             '<(snapshot_test_dart_file)',
           ],
           'message': 'Generating ''<(snapshot_test_dat_file)'' file.'
         },
       ]
     },
   ]
 }