symlink the built .node files into the "build" dir

[TooTallNate]

Sorta solves the problem of "what to require" when you want to conditionally require the Release or Debug build, depending on that was last built.

/cc @tjfontaine

[TooTallNate]

Update: Symlinks require admin privs on Windows so that won't work. Junctions only work on directories on Windows so that doesn't work either. On Windows, we're gonna have to fall back to copying the resulting .node file unfortunately.

[Trott]

This issue is approaching 6 years of inactivity. Should it remain open? (Not saying it should or shouldn't. Just honestly asking. For all I know, the issue has been resolved.)

[bnoordhuis]

I'm not sure what issue this was trying to solve. I'll close it out.