Allow zip64 support when opening zip files

When opening an zip file through zipfile.ZipFile(), python2 by default
disables zip64 support. To support update files >4GB, we manually add
allowZip64 to override the setting.

Test: generate && serve an OTA

Change-Id: I9645e963ced830cc2d3a4b72bc63b9369a1cefe8
diff --git a/tools/releasetools/validate_target_files.py b/tools/releasetools/validate_target_files.py
index 2e3aa74..d2178b2 100755
--- a/tools/releasetools/validate_target_files.py
+++ b/tools/releasetools/validate_target_files.py
@@ -487,7 +487,7 @@
   input_tmp = common.UnzipTemp(args.target_files)
 
   info_dict = common.LoadInfoDict(input_tmp)
-  with zipfile.ZipFile(args.target_files, 'r') as input_zip:
+  with zipfile.ZipFile(args.target_files, 'r', allowZip64=True) as input_zip:
     ValidateFileConsistency(input_zip, input_tmp, info_dict)
 
   CheckBuildPropDuplicity(input_tmp)