Revert "Revert "Add dex file writer to dexlayout tool.""

This reverts commit fd1a6c2a.

Fixed output being clobbered during DexLayoutTest.DexFileOutput.
Option added to put dex output file in scratch directory.

Bug: 29921113
Test: mm test-art-host-gtest-dexlayout_test

Change-Id: I9e6b139cf06aaa39c83ad1e74329db266464a8e4