RFC: subcommand to pause/resume builds

[John Soo]

Hi Guix!

I was looking to pause a long build today and asked on IRC how to
accomplish pause/resume.  It seems this is possible already with the
following:

kill --signal SIGSTOP|SIGCONT {pids-of-build-process-tree}

There is already a command to list the processes associated to guix
commands: guix processes.  Perhaps pause/resume can be a subcommand or
set of flags to guix processes. The following is the first thing that
comes to mind:

guix processes --pause package-name ... --resume package-name ...

What do you think?

Thanks!

- John