(#388) Correctly update to handle three flavours of Microkernel

My previous fix to the handling of the Microkernel flavours used the wrong
build parameter names, to my embarrassment, and my local testing didn't pick
that up as it also used the wrong names.

Hilarity, and this commit, ensue.

Signed-off-by: Daniel Pittman <daniel@rimspace.net>
Merge pull request #398 from daniel-pittman/feature/master/388-handle-updated-internal-package-repo-layout

(#388) Correctly update to handle three flavours of Microkernel