Fix gitdir not being set when cloning. Needed for writing the p4 users cache.

git-p4

@@ -972,6 +972,8 @@ class P4Clone(P4Sync):
         self.needsGit = False
 
     def run(self, args):
+        global gitdir
+
         if len(args) < 1:
             return False
         depotPath = args[0]
@@ -1007,6 +1009,7 @@ class P4Clone(P4Sync):
         os.makedirs(dir)
         os.chdir(dir)
         system("git init")
+        gitdir = os.getcwd()
         if not P4Sync.run(self, [depotPath]):
             return False
         if self.branch != "master":