This also makes shebang always use env command, and drops unnecessary
'bash -c' or 'sh -c' when a signle command is invoked in the shell,
like sleep or echo.
In mkosi, we run the test inside the VM instead of outside. To simplify
the implementation we drop the reboot part and only verify that we can
schedule and cancel shutdowns and that the wall messages are sent as
expected.
Yu Watanabe
Nick Rosbrook
Luca Boccassi
Daan De Meyer