BaseTools: Handle the bytes and str difference

Deal with bytes and str is different, remove the unicode()
Using utcfromtimestamp instead of fromtimestamp.

Cc: Liming Gao <liming.gao@intel.com>
Cc: Yonghong Zhu <yonghong.zhu@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Yunhua Feng <yunhuax.feng@intel.com>
Reviewed-by: Liming Gao <liming.gao@intel.com>

BaseTools/Source/Python/Common/LongFilePathOs.py

@@ -14,7 +14,6 @@
 import os
 from . import LongFilePathOsPath
 from Common.LongFilePathSupport import LongFilePath
-from Common.LongFilePathSupport import UniToStr
 import time
 
 path = LongFilePathOsPath
@@ -63,7 +62,7 @@ def listdir(path):
     List = []
     uList = os.listdir(u"%s" % LongFilePath(path))
     for Item in uList:
-        List.append(UniToStr(Item))
+        List.append(Item)
     return List
 
 environ = os.environ