ART: Allow dex2oat sanitization

Reverts commit c2f0474b.
Reverts commit 07407cd0.

The original commit was made when builds were not preopted by
default, so that dex2oat was speed-compiling everything on first
boot.

Bug: 22233158
Bug: 29188876
Test: m
Test: SANITIZE_TARGET=address m
Test: First boot is acceptable (tested on Pixel)
Change-Id: I52a334c7fe927f78bf8049208e5654e0aa86dbc9