Without passing $HOME into the `sudo` invocation the instance parent
directory detection
(https://github.com/gokrazy/internal/blob/main/instanceflag/instanceflag.go#L19)
fails:
$ gok -i test overwrite --full /dev/sdc
[..]
2023/01/25 22:13:04 partitioning /dev/sdc (GPT + Hybrid MBR)
2023/01/25 22:13:04 Using sudo to gain permission to format /dev/sdc
2023/01/25 22:13:04 If you prefer, cancel and use: sudo setfacl -m u:${USER}:rw /dev/sdc
2023/01/25 22:13:04 open os.UserHomeDir failed: $HOME is not defined/gokrazy/test/config.json: no such file or directory
2023/01/25 22:13:04 exit status 1
This commit does the necessary passing.
Mark DraytonandMichael Stapelberg
