GNUmakefile hardcodes the architectures for which to compile on macOS in the MACOS_COMPILE and MACOS_COMPILE_DEBUG variables. You should make this configurable via another makefile variable. Currently you're hardcoding the architectures i386 and x86_64, but Apple is phasing out 32-bit support and you can't compile for i386 anymore as of the macOS 10.14 SDK.
GNUmakefile hardcodes the architectures for which to compile on macOS in the
MACOS_COMPILE
andMACOS_COMPILE_DEBUG
variables. You should make this configurable via another makefile variable. Currently you're hardcoding the architectures i386 and x86_64, but Apple is phasing out 32-bit support and you can't compile for i386 anymore as of the macOS 10.14 SDK.