Updates to make install_third_party build gtest and gmock on windows.

build_tools/build_utils.py

Index: build_tools/build_utils.py
===================================================================
--- build_tools/build_utils.py	(revision 760)
+++ build_tools/build_utils.py	(working copy)
@@ -79,11 +79,9 @@
 # a fully-qualified absolute path, on Windows it must include the drive letter.
 # |shell_env| describes the environment used by any subprocess (this is
 # normally obtained from GetShellEnvironment()
-# TODO(dspringer,khim): make this work properly for hermetic cygwin (see bug
-# http://code.google.com/p/nativeclient/issues/detail?id=1122)
 def HermeticBuildPath(abs_path, shell_env):
   if (sys.platform == 'win32'):
-    return abs_path
+    return abs_path.replace('\\', '\\\\')
 
   return abs_path