releasetools: make sure we mount/unmount system

Change-Id: I01f33551718aca96f74bb8e9291644e6b74a84fe
props: remove libcamera_metadata, we'll take the built one

Change-Id: I4c94e09d6931600e6410fe4ccf3aab17a1e586fc
m8: update dependencies, remove old flags

Change-Id: I662699a8d23d9ca5b66214386814d3e4d3db6dd0