Pass targetSdkVersion to dex2oat

Dex2oat now accepts targetSdkVersion as a parameter to determine
whether ART should treat the app as "legacy" and allow or restrict
access to private APIs.

We bump the otapreopt argument version to v4 due to the new value.

Bug: 64382372
Test: manual
Change-Id: I5de64e96043404df39f09d3d16b575ee39951fcb