[gn] Fix valgrind config

infra/mb/mb_config.pyl

 # Copyright 2016 The V8 project authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 {
   # This is a map of buildbot master names -> buildbot builder names ->
   # config names (where each config name is a key in the 'configs' dict,
   # below). MB uses this dict to look up which config to use for a given bot.
   # Bots are ordered by appearance on waterfall.
   'masters': {
@@ skipping 526 matching lines @@
       'gyp_defines':
         'release_extra_cflags="-fno-inline-functions -fno-inline"',
     },
 
     'tsan': {
       'gn_args': 'clang=true tsan=true',
       'gyp_defines': 'clang=1 tsan=1',
     },
 
     'valgrind': {
-      # TODO(machenbach): Add this to gn.
-      'gn_args': 'has_valgrind=true',
+      'gn_args': 'v8_has_valgrind=true',
       'gyp_defines': 'has_valgrind=1',
     },
 
     'v8_no_i18n': {
       'gn_args': 'v8_enable_i18n_support=false',
       'gyp_defines': 'v8_enable_i18n_support=0',
     },
 
     'v8_enable_disassembler': {
       'gn_args': 'v8_enable_disassembler=true',
@@ skipping 55 matching lines @@
       'gn_args': 'target_cpu="x64"',
       'gyp_defines': 'target_arch=x64',
     },
 
     'x86': {
       'gn_args': 'target_cpu="x86"',
       'gyp_defines': 'target_arch=ia32',
     },
   },
 }