Motivation for this change

Fix this build toward #28643 .

The issue appears to be that john's Makefile.in depends on AS and LD be set to CC. For example, it assumes that AS can act as a preprocessor and uses commandline options not available in as (like -c or -DAC_BUILT)
See:
https://github.com/magnumripper/JohnTheRipper/blob/f09bb77afcf5d35226cdcad6a64ecfd0caa64e24/src/Makefile.in#L56
https://github.com/magnumripper/JohnTheRipper/blob/f09bb77afcf5d35226cdcad6a64ecfd0caa64e24/src/Makefile.in#L714

By default, their configure script sets AS and LD to CC--which is why this package used to build before recent setup-hook changes. See:
https://github.com/magnumripper/JohnTheRipper/blob/f09bb77afcf5d35226cdcad6a64ecfd0caa64e24/src/configure.ac#L268

Following the discussion in #28106, I've overridden AS and LD to just use CC.

CC @Ericson2314

Things done

• Tested using sandboxing
  (nix.useSandbox on NixOS,
  or option build-use-sandbox in nix.conf
  on non-NixOS)
• Built on platform(s)
  • NixOS
  • macOS
  • Linux
• Tested via one or more NixOS test(s) if existing and applicable for the change (look inside nixos/tests)
• Tested compilation of all pkgs that depend on this change using nix-shell -p nox --run "nox-review wip"
• Tested execution of all binary files (usually in ./result/bin/)
• Fits CONTRIBUTING.md.