Introduce a setting to control the toolset for which d8 is compiled

src/d8.gyp

 # 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 14 matching lines @@
 # (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 # OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 {
   'variables': {
     'v8_code': 1,
     'console%': '',
     # Enable support for Intel VTune. Supported on ia32/x64 only
     'v8_enable_vtunejit%': 0,
     'v8_enable_i18n_support%': 1,
+    'v8_toolset_for_d8%': 'target',
   },
   'includes': ['../build/toolchain.gypi', '../build/features.gypi'],
   'targets': [
     {
       'target_name': 'd8',
       'type': 'executable',
       'dependencies': [
         '../tools/gyp/v8.gyp:v8',
       ],
       # Generated source files need this explicitly:
       'include_dirs+': [
         '../src',
       ],
       'sources': [
         'd8.cc',
       ],
       'conditions': [
+        [ 'want_separate_host_toolset==1', {
+          'toolsets': [ '<(v8_toolset_for_d8)', ],
+        }],
         [ 'console=="readline"', {
           'libraries': [ '-lreadline', ],
           'sources': [ 'd8-readline.cc' ],
         }],
         [ 'component!="shared_library"', {
           'sources': [ 'd8-debug.cc', '<(SHARED_INTERMEDIATE_DIR)/d8-js.cc', ],
           'conditions': [
             [ 'want_separate_host_toolset==1', {
               'dependencies': [
                 'd8_js2c#host',
@@ skipping 63 matching lines @@
             '<@(_outputs)',
             'D8',
             'off',  # compress startup data
             '<@(js_files)'
           ],
         },
       ],
     }
   ],
 }