I have this jailbroken iPhone 3G with iOS version 4.2.1 (the latest supported version). When I connect it to Xcode 4.2, Xcode starts copying the debug symbols. It stops copy
The answer above (https://stackoverflow.com/a/9944892/1390251) works, basically, but for newer versions of Xcode you probably need to rename the files as follows, having them end with '7' instead of '6':
touch .copied_dyld_shared_cache_armv7
touch .processed_dyld_shared_cache_armv7
touch dyld_shared_cache_armv7
If not sure, you can keep both sets of files (...6 and ...7) in the relevant folder (can also be 5.1.1 for that matter) and it should work. (have tested it on iPhone 4 with iOS v5.1.1 genuine)