BaseTools: Fixed issue for IgnoreAutoGen

https://bugzilla.tianocore.org/show_bug.cgi?id=2080

This patch is to improve build -u option to re-use
GlobalVar_<platformguid>_<arch>.bin file which is
introduced by multiple-process-autogen feature.

Cc: Liming Gao <liming.gao@intel.com>
Cc: Steven Shi <steven.shi@intel.com>
Signed-off-by: Bob Feng <bob.c.feng@intel.com>
Acked-by: Liming Gao <liming.gao@intel.com>

BaseTools/Source/Python/AutoGen/PlatformAutoGen.py

@@ -188,7 +188,9 @@ class PlatformAutoGen(AutoGen):
                     Ma.CreateMakeFile(CreateModuleMakeFile, FfsCommand[key])
                 else:
                     Ma.CreateMakeFile(CreateModuleMakeFile)
+        self.CreateLibModuelDirs()
 
+    def CreateLibModuelDirs(self):
         # no need to create makefile for the platform more than once
         if self.IsMakeFileCreated:
             return