Go up to the folder containing the project in your Finder.
Right Click > Get Info
Go to the bottom of the Info pane, and click the little lock, type in your password when prompted.
Then, change permissions for yourself to read+write.
Click the little gear below, and apply to all enclosed items.
Close the lock once you are finished!
If this doesn’t work, Change the value of “Compiler for C/C++/Objective-C” to “Default Compiler (Apple Clang)” under the Build Settings of your target.