Fix permission for public secondary dex files

- make the oat directory accessible by others
- if the dex files is readable by others and we are not doing a speed-
profile compilation make the oat file readable by others.

Bug: 36896515
Test: adb shell cmd package compile -r bg-dexopt  --secondary-dex com.google.android.gms
      check that the oat directory and files have the right permissions

Change-Id: I1829217004353fb8c86e5a6b7eb570555e36a495