comp: fix communication of make exit code

Before this, a typical value of result was 512 when make exited with
2.  os.WEXITSTATUS(512) = 2.  Unfortunately, 'raise SystemExit, 512'
exits with a success code.
comp: it's an error if cd fails
docs: fix spew of AttributeErrors on Ubuntu Hardy
docs: fix spew of AttributeErrors on Ubuntu Hardy

.. for a second time, since the original code didn't work