makeDBusConf: reduce build closure

[vcunat]

*buildInputs take .dev outputs by default, but we don't need it here.
The extra dependency (introduced by commit d172061) was breaking
tests like nixosTests.containers-imperative and nixosTests.installer.*
https://hydra.nixos.org/eval/1767666#tabs-still-fail

[vcunat]

@jtojnar: I can't see why .bin was removed in that commit; maybe it wasn't intentional?

[vcunat]

I did some local tests and then utilized Hydra's idling x86: https://hydra.nixos.org/eval/1767732#tabs-now-succeed

[jtojnar]

Looks like my mental model of mkDerivation was still off. I thought it worked similarly to buildEnv where it does not really matter what output is specified but it turns out (as I understand it now) that evaluation just runs chooseDevOutputs on inputs, and the other outputs are actually picked up at build time from propagated-build-inputs file, when present in the chosen (dev/out/primary) output.

- /nix/store/r9agajdjagf7vq640fql3j3sbhs588wh-dbus-1.drv:{out}
+ /nix/store/l777vhgbiw55iyac56vs2wjqm52n97z4-dbus-1.drv:{out}
• The set of input derivations named `dbus-1.14.0` do not match
• The set of input derivations named `libxslt-1.1.35` do not match
• The environments do not match:
    buildInputs=''
-    /nix/store/f1vf3qp1pbjrrxnskkaxv4hhl7pqf01p-dbus-1.14.0-dev
+    /nix/store/rq558bchx7fscjzl111lwbfi2dlblhxq-dbus-1.14.0
''
    nativeBuildInputs=''
-    /nix/store/xjvn8093khjzwjhn8ixgqjbiwwlpk6w6-libxslt-1.1.35-dev /nix/store/hgwlwph2989gwpzr4dn5qfql168ns194-hook
+    /nix/store/v9awz1pphpb1dbgc1h38i3mj2h3klvsf-libxslt-1.1.35-bin /nix/store/hgwlwph2989gwpzr4dn5qfql168ns194-hook
''

[vcunat]

I checked the multi-out docs. They probably haven't changed significantly for years, but I think they do explain this part OK: https://nixos.org/manual/nixpkgs/stable/#sec-multiple-outputs-using-split-packages