Set compilation reason in vdex-only OatFile.

Test: test.py
Bug: 192408935
Merged-In: Ib87ea546876bfb4c6bf87b60f5a4f8aa306bd186
(cherry picked from commit b17c908047a2df675ecb4bd0aa2b21114376bbae)
Change-Id: I81ea447c12250c24fa88205dac9c1289b15faba8
2 files changed