setup-environment-internal: fix usage when BUILDDIR is unset
setup-environment-internal: fix usage when BUILDDIR is unset

Change-Id: I73f3d16103499685bc084684b573be064661566e
Signed-off-by: Koen Kooi <42e3d96910f922bdd7dd1805fe3f8aff634f391d@dominion.thruhere.net>

Angstrom-distribution/angstrom-manifest