meson option requires config.h for meson options to operate properly

This was removed in
https://github.com/openbmc/phosphor-pid-control/commit/f8b6e55

Change-Id: I42d21365516a104cc0372d1fa72477642784c4d1
Signed-off-by: Pete O_o <pmb@meta.com>
diff --git a/dbus/dbusconfiguration.cpp b/dbus/dbusconfiguration.cpp
index 787ca31..8dcd69b 100644
--- a/dbus/dbusconfiguration.cpp
+++ b/dbus/dbusconfiguration.cpp
@@ -13,6 +13,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 */
+#include "config.h"
 
 #include "dbusconfiguration.hpp"