Makefile: fixed always-out-of-date build b/c of "build" dir target
option.py: typo fix in OptionParser.format_help
HostRunConfig: be a little more flexible w.r.t. __init__ args
Made host-config selection more flexible

Now supports using host aliases etc. for lookup of host config by name.
Makefile: don't make "all" a phony target

If it _is_ phony, Make will re-make everything each time even if it's
up to date.