Add ability to store invocation information in an external file.

It is sometimes useful to save the invocation that generated an odex
file seprately from the file itself. This adds a
--write-invocation-to=<file> flag to dex2oat that lets one do this.

Test: m droid
Test: ./test.py --host -j72
Bug: 119332327
Change-Id: I3fe07e7daba3d27b49fd5b5aed7621e5cc62ab46