Explicitly link against libdl when including TNC support

If you don't choose OpenSSL as TLS implementation and choose to enable
CONFIG_EAP_TNC you have to link against libdl. The OpenSSL libraries
implicitly link against them, so this might be a reason why it wasn't
noticed yet. I assume the same applies to hostapd.

hostapd/Makefile

@@ -335,6 +335,7 @@ CFLAGS += -DEAP_TNC
 OBJS += ../src/eap_server/eap_tnc.o
 OBJS += ../src/eap_server/tncs.o
 NEED_BASE64=y
+LIBS += -ldl
 endif
 
 # Basic EAP functionality is needed for EAPOL

wpa_supplicant/Makefile

@@ -566,6 +566,7 @@ OBJS += ../src/eap_peer/tncc.o
 OBJS_h += ../src/eap_server/eap_tnc.o
 OBJS_h += ../src/eap_server/tncs.o
 NEED_BASE64=y
+LIBS += -ldl
 endif
 
 ifdef CONFIG_IEEE8021X_EAPOL