ensure host compiler is always clang when cross compiling from linux

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 68 matching lines @@
           'gomadir': '<!(/bin/echo -n ${HOME}/goma)',
         }],
       ],
     },
     'host_arch%': '<(host_arch)',
     'target_arch%': '<(target_arch)',
     'v8_target_arch%': '<(v8_target_arch)',
     'werror%': '-Werror',
     'use_goma%': '<(use_goma)',
     'gomadir%': '<(gomadir)',
+    'host_clang%': '1',
 
     # .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,
 
     # Speeds up Debug builds:
     # 0 - Compiler optimizations off (debuggable) (default). This may
     #     be 5x slower than Release (or worse).
@@ skipping 227 matching lines @@
             'cflags': [ '-mminimal-toc' ],
           }],
           [ 'visibility=="hidden" and v8_enable_backtrace==0', {
             'cflags': [ '-fvisibility=hidden' ],
           }],
           [ 'component=="shared_library"', {
             'cflags': [ '-fPIC', ],
           }],
         ],
       },
+      'conditions': [
+        ['clang!=1 and host_clang==1 and target_arch!="ia32" and target_arch!="x64"', {
+          'make_global_settings': [
+            ['CC.host', '../<(clang_dir)/bin/clang'],
+            ['CXX.host', '../<(clang_dir)/bin/clang++'],
+          ],
+        }],
+        ['clang==0 and host_clang==1', {
+          'target_conditions': [
+            ['_toolset=="host"', {
+              'cflags_cc': [ '-std=gnu++11', ],
+            }],
+          ],
+          'target_defaults': {
+            'target_conditions': [
+              ['_toolset=="host"', { 'cflags!': [ '-Wno-unused-local-typedefs' ]}],
+            ],
+          },
+        }],
+      ],
     }],
     # 'OS=="linux" or OS=="freebsd" or OS=="openbsd" or OS=="solaris"
     #  or OS=="netbsd"'
     ['OS=="qnx"', {
       'target_defaults': {
         'cflags': [
           '-Wall',
           '<(werror)',
           '-Wno-unused-parameter',
           '-fno-exceptions',
@@ skipping 192 matching lines @@
     ['use_goma==1 and ("<(GENERATOR)"=="ninja" or clang==1)', {
       'make_global_settings': [
        ['CC_wrapper', '<(gomadir)/gomacc'],
        ['CXX_wrapper', '<(gomadir)/gomacc'],
        ['CC.host_wrapper', '<(gomadir)/gomacc'],
        ['CXX.host_wrapper', '<(gomadir)/gomacc'],
       ],
     }],
   ],
 }