XCode has changed how build settings are made. There are global settings and target settings. These settings can be changed by using the “Inspector” window. This window is context sensitive, so you have to pay attention to what the inpector window is actually inspecting.
To modify project “global” settings, select the project group (this group will be the top most group, in the Groups & Files list, named after the project - see figure below). Right Click or Control Plus Click (RCCPC) on the selected project group and then select the menu item “Show Inspector”.
To modify target settings, select the target by clicking on the “Target” group’s disclosure triangle and then select the group named after the target you wish to edit. RCCPC on the selected target and then select the menu item “Show Inspector”.
The link below has useful information on XCode build settings.