c_abi: when compiling for x86_64, differenciate between system V and windows ABI
c_abi: when compiling for x86_64, differenciate between system V and windows ABI

raulgrell/zig,andrewrk/zig,raulgrell/zig,raulgrell/zig,raulgrell/zig,andrewrk/zig,raulgrell/zig,zig-lang/zig,zig-lang/zig,zig-lang/zig