v8: fix dragonflybsd build

tools/gyp/v8.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 669 matching lines @@
                     ]
                   }],
                 ],
               },
             ],
             ['OS=="freebsd"', {
                 'link_settings': {
                   'libraries': [
                     '-L/usr/local/lib -lexecinfo',
                 ]},
+            }],
+            ['OS=="dragonflybsd"', {
+                'link_settings': {
+                  'libraries': [
+                    '-pthread',
+                ]},
+            }],
+            ['OS=="freebsd" or OS=="dragonflybsd"', {
                 'sources': [
                   '../../src/platform-freebsd.cc',
                   '../../src/platform-posix.cc'
                 ],
               }
             ],
             ['OS=="openbsd"', {
                 'link_settings': {
                   'libraries': [
                     '-L/usr/local/lib -lexecinfo',
@@ skipping 307 matching lines @@
             }],
           ],
           'dependencies': [
             'v8'
           ],
         },
       ],
     }],
   ],
 }