Use icu_gyp_path variable to reference ICU gyp file

build/standalone.gypi

 # Copyright 2012 the V8 project authors. All rights reserved.
 # Redistribution and use in source and binary forms, with or without
 # modification, are permitted provided that the following conditions are
 # met:
 #
 #     * Redistributions of source code must retain the above copyright
 #       notice, this list of conditions and the following disclaimer.
 #     * Redistributions in binary form must reproduce the above
 #       copyright notice, this list of conditions and the following
 #       disclaimer in the documentation and/or other materials provided
@@ skipping 59 matching lines @@
     'target_arch%': '<(target_arch)',
     'v8_target_arch%': '<(v8_target_arch)',
     'werror%': '-Werror',
 
     # .gyp files or targets should set v8_code to 1 if they build V8 specific
     # code, as opposed to external code.  This variable is used to control such
     # things as the set of warnings to enable, and whether warnings are treated
     # as errors.
     'v8_code%': 0,
 
+    # Relative path to icu.gyp from this file.
+    'icu_gyp_path': '../third_party/icu/icu.gyp',
+
     'conditions': [
       ['(v8_target_arch=="arm" and host_arch!="arm") or \
         (v8_target_arch=="mipsel" and host_arch!="mipsel") or \
         (v8_target_arch=="x64" and host_arch!="x64") or \
         (OS=="android")', {
         'want_separate_host_toolset': 1,
       }, {
         'want_separate_host_toolset': 0,
       }],
       ['OS == "win"', {
@@ skipping 186 matching lines @@
         },
         'target_conditions': [
           ['_type!="static_library"', {
             'xcode_settings': {'OTHER_LDFLAGS': ['-Wl,-search_paths_first']},
           }],
         ],  # target_conditions
       },  # target_defaults
     }],  # OS=="mac"
   ],
 }