The build thread owns the TTY in the current setup. To keep the update
and build processess from fighting over the TTY when in async mode,
we've been simply squelching the update output up to this point, except
for errors.
This is not really the best idea as it can leave out kind of important
details. With this change we configure the logging subsystem to forward
its messages that it would ordinarily print out to instead go over an
IPC channel.
The IPC channel knows which module is currently being operated on, tags
the message, and forwards it over to destination proc's IPC handler,
which extracts it and holds onto the message until that proc reaches the
same module.
Once the receiver proc is processing the module, those messages are all
output at once and then normal processing resumes.
In case some messages are never read out this way (e.g. a module is
updated but never built) we have a message scavenger right after the
build is done to give those messages as well.
This can be used as a run-time check later to ensure that kdesrc-build
finds compatible versions of its component modules (though that isn't
done yet).
Michael Pyne