Fix debuggable compiler flag detection for secondary dex files

Compiles secondary dex files like the primary dex file: if it has
been compiled with the --debuggable flag, compile secondary dex files
with the --debuggable flag too.

Therefore, dex files loaded at runtime are compiled the same way as
dex files compiled at install time on the classpath (excluding the
boot image that is not compiled debuggable).

Also adds debuggable key in the oat header and bump the oat version.

Bug: 20944228
Change-Id: I59119f3468adb27ab1d6026f2cefbebbd814224c