TODO

Right now, I don't think we're really handling switching config options
properly.  If we enable/disable individual components, dependencies using
those components need to be reset - their old compiles will no longer be
valid if one of their dependencies changes.  We need to:

1.  clear the bext_output directory, so the contents reflect the new
    settings rather than keeping potentially outdated files

2.  remove old build directory contents for those projects that have
    had a dependency change status, so their compiles end up detecting
    and linking to the correct versions.  We can't depend on third
    party build systems to reset everything correctly, so we need to
    start clean.