Use native ISA for dex code (in case there's a NativeBridge)

In the presence of a native bridge it is more efficient to compile the
dex directly to the native ISA than to use the shared library ISA as a
reference.

This can be achieve by configuring the readonly system properties to map
between the .so ISA and the desired dex code .ISA (e.g.
ro.dalvik.vm.isa.ISA1=ISA2).

Bug: 16185267

Change-Id: I50baa7b37e1465b9adf72d6f6b96f526a08d59c7