fix(tvix/tests/tvix-init): run as pid1, support init= r/6651

We were previously not running as PID1, but were executing things via
uinitcmd (by u-root init).
This had some problems - a real system pid1 really wants to be pid1.

u-root init itself seems to be too complicated to configure as a
chainloader, so instead, we just provide init/pid1 ourselves and do the
little bit of mount setup / stage 1 that's necessary.

`tvix.exec` is renamed to `tvix.run`, to further distinguish it from the
`exec` bash function.

Our init will now also power off the machine if the shell, or the custom
tvix.run command finished. In the case of switch_root (`init=` being
passed), we terminate before, so it's up to the real system anyways.

Change-Id: If00c0c11ca9393968e76ae0d131594b5c135fa48
Reviewed-on: https://cl.tvl.fyi/c/depot/+/9454
Autosubmit: flokli <flokli@flokli.de>
Reviewed-by: Connor Brewster <cbrewster@hey.com>
Tested-by: BuildkiteCI

0 files changed, 0 insertions, 0 deletions