Implement islink, readlink and realpath using Win32 api

Change-Id: I18452cbb32d24db73601ad10485dbe6bb278731c
diff --git a/subcmds/sync.py b/subcmds/sync.py
index b88c596..93fea23 100644
--- a/subcmds/sync.py
+++ b/subcmds/sync.py
@@ -498,7 +498,7 @@
       dirs_to_remove += [os.path.join(root, d) for d in dirs
                          if os.path.join(root, d) not in dirs_to_remove]
     for d in reversed(dirs_to_remove):
-      if os.path.islink(d):
+      if platform_utils.islink(d):
         try:
           os.remove(d)
         except OSError: