Fix OS X build

- Use $(uname) instead of $OSTYPE
- Fix shebang
- Fix typo

The OS X build failures (caused by the wrong `$OSTYPE` env var) were originally reported at:
https://github.com/openshift/origin/issues/177

Signed-off-by: Vojtech Vitek (V-Teq) <vvitek@redhat.com>
Yeah, it worked for me as well. But some guys reported having `$OSTYPE=Linux` on OS X probably because of macports or something..