Write dexpreopt.config again during the build

Writing $OUT/dexpreopt.config during build setup and then using
it during the build causes bad incremental builds if a cleanspec
removes $OUT/dexpreopt.config.  Create a rule in Soong to write
out a copy so that it is a normal build artifact.

Bug: 132379813
Test: m checkbuild
Change-Id: I7755a7f8c1d6561fc83022a7f4cf7e4a64e989c9