http://www.haage-partner.de/download/AmigaOS/NDK39.lha is the link to the AmigaOS 3.9 includes if you need to do it manually.
https://github.com/bebbo/amiga-gcc/b...ster/README.md has dependency information for 3 environments but Homebrew or MacPorts for macOS aren't among them. Milage may vary depending on how familiar you are with your Mac environment.