Log Message:
Fix build:

1. "unzip -x file.zip" does not work with any unzip I can find; drop
the -x.

2. Because there's a self-extracting archive, NetBSD's builtin unzip
doesn't work. When ${OPSYS} is NetBSD, explicitly depend on
archivers/unzip instead of adding unzip to USE_TOOLS. (I'm not sure
this is the right way to go about this. It at least works though.)