Update V8 to r5388 as required by WebKit r66666

Change-Id: Ib3c42e9b7226d22c65c7077c543fe31afe62a318
diff --git a/tools/utils.py b/tools/utils.py
index 3a55722..8083091 100644
--- a/tools/utils.py
+++ b/tools/utils.py
@@ -63,14 +63,20 @@
     return None
 
 
+# This will default to building the 32 bit VM even on machines that are capable
+# of running the 64 bit VM.  Use the scons option --arch=x64 to force it to build
+# the 64 bit VM.
 def GuessArchitecture():
   id = platform.machine()
+  id = id.lower()  # Windows 7 capitalizes 'AMD64'.
   if id.startswith('arm'):
     return 'arm'
-  elif (not id) or (not re.match('(x|i[3-6])86', id) is None):
+  elif (not id) or (not re.match('(x|i[3-6])86$', id) is None):
     return 'ia32'
   elif id == 'i86pc':
     return 'ia32'
+  elif id == 'x86_64':
+    return 'ia32'
   elif id == 'amd64':
     return 'ia32'
   else: