bug#60106: [Shepherd 0.9.3] ‘system*’ replacement cannot be passed environment variables

[Adam Faiz]

> I think we’ll have to add a parameter to ‘spawn-command’ to specify
> environment variables.
>
> Ludo’.
If you do this, can you add an #:append? flag which adds environment 
variables to the inherited environment instead of specifying the 
variables declaratively? It can be #f by default.

It would be very useful for me using the shepherd as init on a foreign 
distro, so I don't have to use the `env` command.