We previously weren't able to build systemd for Musl, but now we can! (But not statically.) So there's no longer any reason to have systemd support in Redis disabled by default for pkgsMusl.
···1{ lib, stdenv, fetchurl, lua, pkg-config, nixosTests
2-, withSystemd ? stdenv.isLinux && !stdenv.hostPlatform.isMusl, systemd
3# dependency ordering is broken at the moment when building with openssl
4, tlsSupport ? !stdenv.hostPlatform.isStatic, openssl
5}:
···1{ lib, stdenv, fetchurl, lua, pkg-config, nixosTests
2+, withSystemd ? stdenv.isLinux && !stdenv.hostPlatform.isStatic, systemd
3# dependency ordering is broken at the moment when building with openssl
4, tlsSupport ? !stdenv.hostPlatform.isStatic, openssl
5}: