I was missing some GCC 4.2 options (such as a nice way to do some preprocessor definitions) in an older project of mine, and I knew that I had done something similar on a newer project.
As it turns out, for some reason it seems to put these options back in the Project Info window if you change your Code Signing Identity option. I changed it (and the Any iOS option below it) to a different profile, then changed them back to iPhone Developer, and the missing options suddenly appeared in my older project.
Here is a link to the Stack Overflow question and answer:
Missing GCC 4.2 options in Project Info / Build tab in Xcode 3.2.5
By the way, Happy New Year everyone. I hope you all had a nice 2010 holiday season.