Attempt at making git-drover work on Windows

BUG=404755
R=sammc@chromium.org

Review URL: https://codereview.chromium.org/1387223002

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@297055 0039d316-1c4b-4281-b951-d872f2087c98
diff --git a/git_common.py b/git_common.py
index 5a01c83..d405144 100644
--- a/git_common.py
+++ b/git_common.py
@@ -821,10 +821,12 @@
 
 
 def make_workdir_common(repository, new_workdir, files_to_symlink,
-                        files_to_copy):
+                        files_to_copy, symlink=None):
+  if not symlink:
+    symlink = os.symlink
   os.makedirs(new_workdir)
   for entry in files_to_symlink:
-    clone_file(repository, new_workdir, entry, os.symlink)
+    clone_file(repository, new_workdir, entry, symlink)
   for entry in files_to_copy:
     clone_file(repository, new_workdir, entry, shutil.copy)