Interrupting and resuming the "Building" phase?

[Adam Funk]

I'm trying to do `sudo port install ghc` on my old PowerBook and it's
taking longer than I can leave the laptop sitting around to do it.  I
tried hitting Ctl-C and then running the same command again (this
always worked when fink, which I recently switched from, was building
from source packages) but I just get an insurmountable error (as far
as I can tell) and have to start over again.

I know that normally make-driven builds can be interrupted and
resumed, but I'm new to MacPorts.  How can I do this?

Thanks,
Adam