Not sure what the intent was expecting help.sh to fail in the main suite, but it caused `meson test` to fail inside a `nix develop` shell:
$ meson test help --print-errorlogs
ninja: Entering directory `/home/eelco/Dev/nix-master/build'
1/1 nix-functional-tests:main / help UNEXPECTEDPASS 4.02s
Without the change `meson setup` fails on `Gentoo or Debian as those
don't use multicall binary:
$ meson setup ..
...
Executing subproject nix-functional-tests
...
../src/nix-functional-tests/meson.build:24:14: ERROR: Program 'coreutils' not found or not executable
The change always uses `ls` to look `coreutils` up.
Closes: https://github.com/NixOS/nix/issues/11975
