How to make kernel.dev include other `rust/*` files in the `/source` directory?

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1

For developing rust kernel modules, there are some useful targets in .../source/rust/Makefile, but when I list the rust directory I get:

$ ls "$(nix build nixpkgs#linuxPackages.kernel.dev --no-link --print-out-paths)/lib/modules/6.12.26/source/rust"
total 8
dr-xr-xr-x 2 root root 4096 Jan  1  1970 bindings
dr-xr-xr-x 2 root root 4096 Jan  1  1970 uapi

Note that:

$ nix eval nixpkgs#linuxPackages.kernel.withRust
true

Currently, to get access to the source I am just doing it directly via:

kernelsrc = pkgs.runCommandCC "kernelsrc" { } ''
  mkdir $out
  tar -xvf ${kernel.src} -C $out --strip-components=1
''

Which gives me access to the files as listed here.