Codesign Problems in Mountain Lion

[Chirson]

I have been searching for a solution to my problem for a while and not finding suitable one I decided to start a new thread here. First, I'd like to state that I'm not a developer and I don't have Xcode installed on my machine. What I want is occasionally to be able to change app icon and not receive annoying firewall messages to allow incoming connections every time I start the app. Up until 10.7 when I did this I would re-codesign the app in terminal creating my own certificate in keychain and fix this issue. However in 10.8 when I try to do this I receive an error: object file format unrecognised, invalid, or unsuitable. Searching the net I found thread here explaining that installing latest version of Xcode and some additional command line tools from apple developers website solves this problem for registered developers but no word for people like me. Any help is appreciated.