BaseTools: Use absolute import in Common

Based on "futurize -f libfuturize.fixes.fix_absolute_import

Contributed-under: TianoCore Contribution Agreement 1.1
Cc: Yonghong Zhu <yonghong.zhu@intel.com>
Cc: Liming Gao <liming.gao@intel.com>
Signed-off-by: Gary Lin <glin@suse.com>
Reviewed-by: Jaben Carsey <jaben.carsey@intel.com>

BaseTools/Source/Python/Common/LongFilePathOs.py

@@ -11,8 +11,9 @@
 # WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
 #
 
+from __future__ import absolute_import
 import os
-import LongFilePathOsPath
+from . import LongFilePathOsPath
 from Common.LongFilePathSupport import LongFilePath
 from Common.LongFilePathSupport import UniToStr
 import time