fix up ota_from_target_files symlink detection.

Change-Id: I10b668096d4e61e75473dd805f96387049f29b79

tools/releasetools/ota_from_target_files.py

@@ -136,12 +136,12 @@ def MostPopularKey(d, default):
 def IsSymlink(info):
   """Return true if the zipfile.ZipInfo object passed in represents a
   symlink."""
-  return (info.external_attr >> 16) == 0o120777
+  return (info.external_attr >> 16) & 0o770000 == 0o120000
 
 def IsRegular(info):
   """Return true if the zipfile.ZipInfo object passed in represents a
-  symlink."""
-  return (info.external_attr >> 28) == 0o10
+  regular file."""
+  return (info.external_attr >> 16) & 0o770000 == 0o100000
 
 def ClosestFileMatch(src, tgtfiles, existing):
   """Returns the closest file match between a source file and list