Do not use realpath in oat file assistant

Installd logic was updated to compile secondary dex
files next to their specified loading path (instead of the realpath).
It simplifies cleaning secondary dex files artifacts from sym link
locations.

Bug: 64460009
Test: m test-art-host-gtest
Change-Id: I79aea4932672c6c25aff8e03136efef39bc93fe6