UE 4 has some code that modern toolchains flag with warnings, but since the build has “warnings as errors” turned on by default, this causes the build to fail.
Three options:
- Switch to developing in Unreal Engine 5 instead (any particular reason why you’re still preferring 4?).
- Configure the build settings to suppress these warnings (see: https://forums.unrealengine.com/t/wdeprecated-builtins-error-when-trying-to-build-ue4-on-xcode-15-0-1 – I know that this issue was reported for Xcode but the solution should be the same as for you).
- Fix the errors in the Unreal Engine source and compile your own build of the engine (this is hard, especially given that 4.27 is now more than 3 years old so there’s less support out there for it if you get stuck).