[oe] Cleaning up SDK/Toolchain

[Graeme Gregory]

> > That would be a better approach. Graeme, do you still want to have a
> > shot at implementing a unionfs based approach?
> 
> Hmm. Does that need root privs?
> 
Not what I was thinking, which was to do a union via LD_PRELOAD
basically redirecting open and its friends. I once saw a program that
did this trick tomorrow I shall try and dig it out, and try and give
it a few simple tests.

Graeme