Add a postinstall script for GC on F2FS

This script is intended to run on F2FS checkpointing devices.
It triggers garbage collection for a period of time to make
mounting with checkpoint=disable smoother.

Test: Set this script as a postinstall script on vendor
Bug: 123367711
Change-Id: I87e143a2004da5852654688c3c8773510b7073ae
2 files changed