Fix FTBFS due to missing link to stdc++

(cherry picked from commit ee832586c4)

src/Makefile

@@ -19,7 +19,7 @@ ckpasswd: ckpasswd.o
 	gcc ckpasswd.o xmalloc.o messages.o -o ckpasswd -lpam -lcrypt
 
 smartauthmon: smartauthmon.o ckpass.o
-	gcc smartauthmon.o ckpass.o xmalloc.o messages.o -o smartauthmon -lqt-mt -ltqt -lpam -lcrypt
+	gcc smartauthmon.o ckpass.o xmalloc.o messages.o -o smartauthmon -lqt-mt -ltqt -lpam -lcrypt -lstdc++
 
 clean: 
 	rm -f ckpasswd.o xmalloc.o messages.o ckpasswd