hiding “guix system” messages

[Ricardo Wurmus]

Hi Guix,

when installing / building / reconfiguring a system, Guix spawns a few
tools that produce output that might be confusing or misleading.  One
example is the output of the GRUB installation, which says things like
“Installation finished. No error reported.” or that it’s installing
something for a 386 system.

I think we should hide (redirect to a log file) or at least prefix
messages that are produced by tools that Guix spawns.  We could then
deliberately print messages that indicate the “phases” of installing the
system, such as “Installing GRUB…”, “Creating user accounts…”, etc.

What do you think?

--
Ricardo