The problem was initially noticed in https://sourceware.org/PR30052#c5 where 'runtest' was passing bogus target name when ran without parameters:

$ ./result/bin/runtest
...
Target is .runtest-wrapped
Host   is x86_64-pc-linux-gnu

Note that runtest switches to non-native mode and uses wrapper name as a target name. Mechanics of it is a bit involved: 'runtest' itself detects targets passing via ${0} parameter:

# somewhere in runtest:
mypath=${0-.}
...
if [ "$target" != runtest ] ; then
    target="--target ${target}"
else
    target=""
fi

which would be fine if we ran 'runtest'.

In nixpkgs runtest is a shell wrapper:

$ cat /<<NIX>>/dejagnu-1.6.3/bin/runtest
#! /<<NIX>>/bash-5.2-p15/bin/bash -e
...
exec -a "$0" "/<<NIX>>/dejagnu-1.6.3/bin/.runtest-wrapped"  "$@"

You would expect that .runtest-wrapped would get $0 as an argv[0] here, but no. If both are bash scripts bash peeks original argv[0] and breaks runtest:

https://lists.gnu.org/archive/html/bug-bash/2023-01/msg00082.html

The workaround here is to drop the wrapper and place expect symlink into a place where dejagnu and runtest expect it to be without a wrapper creation.

Description of changes

Things done

• Built on platform(s)
  • x86_64-linux
  • aarch64-linux
  • x86_64-darwin
  • aarch64-darwin
• For non-Linux: Is sandbox = true set in nix.conf? (See Nix manual)
• Tested, as applicable:
  • NixOS test(s) (look inside nixos/tests)
  • and/or package tests
  • or, for functions and "core" functionality, tests in lib/tests or pkgs/test
  • made sure NixOS tests are linked to the relevant packages
• Tested compilation of all packages that depend on this change using nix-shell -p nixpkgs-review --run "nixpkgs-review rev HEAD". Note: all changes have to be committed, also see nixpkgs-review usage
• Tested basic functionality of all binary files (usually in ./result/bin/)
• 23.05 Release Notes (or backporting 22.11 Release notes)
  • (Package updates) Added a release notes entry if the change is major or breaking
  • (Module updates) Added a release notes entry if the change is significant
  • (Module addition) Added a release notes entry if adding a new NixOS module
  • (Release notes changes) Ran nixos/doc/manual/md-to-db.sh to update generated release notes
• Fits CONTRIBUTING.md.