darkstat: Depend on libbsd for glibc-based toolchains

darkstat's configure script searches for libbsd for different routines,
so if it manages to pick it up, make sure the dependency is reflected.

Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>

net/darkstat/Makefile

@@ -27,7 +27,7 @@ include $(INCLUDE_DIR)/package.mk
 define Package/darkstat
   SECTION:=net
   CATEGORY:=Network
-  DEPENDS:=+libpcap +zlib
+  DEPENDS:=+libpcap +zlib +USE_GLIBC:libbsd
   TITLE:=Network bandwidth monitor
   URL:=http://unix4lyfe.org/darkstat/
 endef