Keep using gdb (not gdb-apple) and just do the following steps:
1- Create a certificate:
- Start Keychain Access application (/Applications/Utilities/Keychain Access.app)
- Open menu /Keychain Access/Certificate Assistant/Create a Certificate...
- Choose a name (gdb-cert in the example), set Identity Type to "Self Signed Root", set Certificate Type to "Code Signing" and select the "Let me override defaults".
- Click several times on Continue until you get to the Specify a Location For The Certificate screen, then set Keychain to System.
- Using the contextual menu for the certificate, select "Get Info", open the Trust item, and set Code Signing to "Always Trust".
2- You must quit Keychain Access application (named "taskgated",from activity monitor) and open it again in order to use the certificate.
3- Assign the certificate to gdb:
- using the following command:
$ codesign -s gdb-cert gdb
For more details, check this link: http://sourceware.org/gdb/wiki/BuildingOnDarwin
if any of these steps are not clear, feel free to ask.