Set the timestamp of dex2oat metrics to SystemClock.uptimeMillis()

This will allow us to inspect whether or not compilation times
degrade over time.

Test: ArtStatsLogUtilsTest
Bug: 170149255
Merged-In: I3a0946b4e2bba32db3c972a871bbd2519d1d70c3
Change-Id: I3a0946b4e2bba32db3c972a871bbd2519d1d70c3
(cherry picked from commit 4c75ae6c23e362f8f591c9dc7831f30d91e98e91)
1 file changed