Handle RawData case for DexLayout

For vdex, the RawData dex file source is used. This was not
compatible with the existing LayoutAndWriteDexFile code. Added
handling to support RawData sources.

Without the handing, it was incorrectly using GetRawFile and casting
the dex file header to a File* causing a bogus fd number.

Test: adb shell cmd package compile -a --reset
Test: adb shell cmd package compile -a -m speed-profile
Test: test-art-host

Bug: 35761072
Change-Id: I74bdd17295479058e9245d1defb132df40fff474