Use clang as default host compiler when cross-compiling

build/set_clang_warning_flags.gypi

 # Copyright (c) 2014 The Chromium 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 file is meant to be included to set clang-specific compiler flags.
 # To use this the following variable can be defined:
 #   clang_warning_flags:       list: Compiler flags to pass to clang.
 #   clang_warning_flags_unset: list: Compiler flags to not pass to clang.
 #
 # Only use this in third-party code. In chromium_code, fix your code to not
@@ skipping 28 matching lines @@
         'WARNING_CFLAGS': ['>@(clang_warning_flags)'],
         'WARNING_CFLAGS!': ['>@(clang_warning_flags_unset)'],
       },
       'msvs_settings': {
         'VCCLCompilerTool': {
           'AdditionalOptions': [ '>@(clang_warning_flags)' ],
           'AdditionalOptions!': [ '>@(clang_warning_flags_unset)' ],
         },
       },
     }],
+    ['clang==0 and host_clang==1', {
+      'target_conditions': [
+        ['_toolset=="host"', {
+          'cflags': [ '>@(clang_warning_flags)' ],
+          'cflags!': [ '>@(clang_warning_flags_unset)' ],
+        }],
+      ],
+    }],
   ],
 }