I'm following this tutorial: https://littleosbook.github.io/#linking-the-kernel

and I'm on a Mac. I'm at the point where I have an object file created from nasm, and I want to turn it into an ELF

I wanted to build a cross-compiler for MacOS X that would allow me to compile the ELF kernel image of my tiny operating system I’m developing without having to always use my Arch Linux distribution instead of just using OS X. Creating a cross-compiler is not that hard, but it requires following some instructions and it takes some time. The good thing is that once you build it, you can leave it in a folder installed and you won’t ever have to build it again. In this article I’ll describe how I compiled myself the i386-elf-gcc compiler on MacOS X El Capitan.