David Dubbeldam
The Apple M1 chip is based on the ARM instruction set. To compile for the M1, add the target flag to the llvm compiler
-target arm64-apple-macos11 -mmacosx-version-min=11.0
To compile for x86_64 on the Apple M1 use the following flag
-arch x86_64
#if arch(arm64)
// Code meant for the arm64 architecture here.
#elseif arch(x86_64)
// Code meant for the x86_64 architecture here.
#endif
To see the architectures present in a built executable file, run the lipo command-line tool
lipo -archs executable
To generate an universal binary, use the lipo command-line tool
lipo -create -output universal_executable x86_executable arm_executable
Note that the same command applies to generate universal static libraries.