package/sslh: systemd needs libconfig

systemd-sslh-generator unconditionally uses libconfig

Fixes:
 - http://autobuild.buildroot.org/results/d46581842906f7780f4a3a1ae21963e78e7f5276

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
[yann.morin.1998@free.fr:
  - select libconfig
  - drop changes in the .mk
]
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>
diff --git a/package/sslh/Config.in b/package/sslh/Config.in
index e608586..f6b46f3 100644
--- a/package/sslh/Config.in
+++ b/package/sslh/Config.in
@@ -1,7 +1,7 @@
 config BR2_PACKAGE_SSLH
 	bool "sslh"
-	# uses fork()
-	depends on BR2_USE_MMU
+	depends on BR2_USE_MMU # fork()
+	select BR2_PACKAGE_LIBCONFIG if BR2_PACKAGE_SYSTEMD
 	help
 	  Applicative protocol multiplexer