syslogng: fix build failure related to setuptools

[pmiddend]

Description of changes

Latest unstable syslogng fails with this error (see hydra):

syslog-ng> /nix/store/a1s263pmsci9zykm5xcdf7x9rv26w6d5-bash-5.2p26/bin/bash /build/source/install-sh -d //nix/store/3r2gf24fyqk3g2w8wdj3mx0i4x038vkg-syslog-ng-4.6.0/share/syslog-ng/include/scl
syslog-ng> Traceback (most recent call last):
syslog-ng>   File "/build/source/modules/python-modules/setup.py", line 24, in <module>
syslog-ng>     from setuptools import setup
syslog-ng> ModuleNotFoundError: No module named 'setuptools'

So setuptools was missing, I added it, now it builds.

Things done

• Built on platform(s)
  • x86_64-linux
  • aarch64-linux
  • x86_64-darwin
  • aarch64-darwin
• For non-Linux: Is sandboxing enabled in nix.conf? (See Nix manual)
  • sandbox = relaxed
  • sandbox = true
• 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/)
• 24.05 Release Notes (or backporting 23.05 and 23.11 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
• Fits CONTRIBUTING.md.

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[vifino]

Why did it build before without issues?
Regardless, this seems like a working fix.