make-dbus-conf: Use libxslt.bin instead of .dev

The problem with using libxslt as buildInputs is that the dev output is
used for building the dbus config.

This is one of the reasons why the installer tests are failing since
ac0cdc19

, because the tests do not have
libxslt.dev in their closure and really shouldn't.

Signed-off-by: aszlig <aszlig@redmoonstudios.org>
Cc: @abbradar