build 64 bit code on x86_64, see upstream
http://code.google.com/p/v8/issues/detail?id=429

--- a/tools/utils.py
+++ b/tools/utils.py
@@ -67,12 +67,17 @@
   id = platform.machine()
   if id.startswith('arm'):
     return 'arm'
-  elif (not id) or (not re.match('(x|i[3-6])86', id) is None):
-    return 'ia32'
   elif id == 'i86pc':
     return 'ia32'
   elif id == 'amd64':
     return 'ia32'
+  elif id == 'x86_64':
+    return 'x64'
+  elif id == 'mipsel':
+    # only little endian is supported as of libv8 2.2.24
+    return 'mips'
+  elif (not id) or (not re.match('(x|i[3-6])86', id) is None):
+    return 'ia32'
   else:
     return None