Split out minimal ART dexpreopt config and use it in mainline builds.

The config sets a few system properties that end up in command-line
arguments passed to dex2oat. Without these properties dex2oat invocation
fails, because options -Xms and -Xmx are do not have an argument.

Test: buid_mainline_modules.sh
Bug: 176171716
Change-Id: I4fd1f059aad5d48495948bfd668307de8b3d9ee1