Set clang directory in gyp.

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 15 matching lines @@
 # OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 # Definitions to be used when building stand-alone V8 binaries.
 
 {
   # We need to include toolchain.gypi here for third-party sources that don't
   # directly include it themselves.
   'includes': ['toolchain.gypi'],
   'variables': {
     'component%': 'static_library',
+    'make_clang_dir%': '../third_party/llvm-build/Release+Asserts',
+    'clang_xcode%': 0,
     'asan%': 0,
     'tsan%': 0,
     'visibility%': 'hidden',
     'v8_enable_backtrace%': 0,
     'v8_enable_i18n_support%': 1,
     'v8_deprecation_warnings': 1,
     'msvs_multi_core_compile%': '1',
     'mac_deployment_target%': '10.5',
     'variables': {
       'variables': {
@@ skipping 379 matching lines @@
             },
           }],
         ],
         'target_conditions': [
           ['_type!="static_library"', {
             'xcode_settings': {'OTHER_LDFLAGS': ['-Wl,-search_paths_first']},
           }],
         ],  # target_conditions
       },  # target_defaults
     }],  # OS=="mac"
+    ['clang==1 and ((OS!="mac" and OS!="ios") or clang_xcode==0) '
+        'and OS!="win"', {
+      'make_global_settings': [
+        ['CC', '<(make_clang_dir)/bin/clang'],
+        ['CXX', '<(make_clang_dir)/bin/clang++'],
+        ['CC.host', '$(CC)'],
+        ['CXX.host', '$(CXX)'],
+      ],
+    }],
+    ['clang==1 and OS=="win"', {
+      'make_global_settings': [
+        # On Windows, gyp's ninja generator only looks at CC.
+        ['CC', '<(make_clang_dir)/bin/clang-cl'],
+      ],
+    }],
   ],
 }