Prevent spurious dexopts in 32-64 builds.

When we're checking if a file needs to be dexopted, we
need to compare oat file checksums with the image checksum
for the oat file's target instruction set and not the current
runtime's target instruction set.

bug:14475807

Change-Id: Ib44d8e3c6cdf3a37fce6332c694a6602c658e925
5 files changed