[plt-scheme] mzc --gui-exe on OSX/v299.22

A quick question today:

Using a recent (within the week) CVS snapshot of v299, I decided to play 
around with mzc and the --gui-exe option. This creates what looks like a 
valid OSX app bundle, but ... OSX seems to think it's just another 
folder. Suggestions? I think I'm running 10.3.6 at this point.

Truth told, I've only recently discovered how great mzc is, as it has 
already simplified a number of things I was doing across several 
platforms (Mac, Solaris, Windows, etc.). Being able to bundle and ship a
"binary" is great. Thanks.

M