What?

Files required to build Linux kernel on macOS.

How?

Not that hard. Install all the GNU tools and make sure they're used:

brew install findutils coreutils gnu-tar gnu-sed make

export PATH="/usr/local/opt/findutils/libexec/gnubin:/usr/local/opt/coreutils/libexec/gnubin:/usr/local/opt/gnu-tar/libexec/gnubin:/usr/local/opt/gnu-sed/libexec/gnubin:/usr/local/opt/make/libexec/gnubin:$PATH"

For make menuconfig you need ncurses:

brew install ncurses

export PKG_CONFIG_PATH="$PKG_CONFIG_PATH:/usr/local/opt/ncurses/lib/pkgconfig"

Install the elf.h header:

brew install nsabovic/linuxonmac/elf-header

Then build the kernel. make menuconfig should work. You may run into issues where kernel calls /bin/false, which won't work since macOS has it in /usr/bin/false. I suggest just replacing these calls in the Makefiles.