add tail

Makefile

@@ -1,8 +1,10 @@
 include config.mk
 
-LIB = util/afgets.o util/agetcwd.o util/enmasse.o util/eprintf.o util/recurse.o
+LIB = util/afgets.o util/agetcwd.o util/concat.o util/enmasse.o util/eprintf.o \
+      util/recurse.o
 SRC = basename.c cat.c chown.c date.c dirname.c echo.c false.c grep.c head.c \
-      ln.c ls.c mkdir.c mkfifo.c pwd.c rm.c sleep.c tee.c touch.c true.c wc.c
+      ln.c ls.c mkdir.c mkfifo.c pwd.c rm.c sleep.c tail.c tee.c touch.c \
+      true.c wc.c
 OBJ = $(SRC:.c=.o) $(LIB)
 BIN = $(SRC:.c=)
 MAN = $(SRC:.c=.1)