Fix a couple of minor problems

The second problem, where it can't find the core module in the repl, I ran into before I figured out that the <magpie_repo>/magpie script was expecting build output in <magpie_repo>/build/, instead of <magpie_repo>/out/, where the default makefile build on OS X puts it. I'm not sure how to fix that problem.

Here's the command I used to generate the Makefile (I don't like xcode):
./dep/gyp/gyp --depth=./ -Dlibrary=static_library -Icommon.gypi --format=make