iproute2 - Fix up and simplify variables pointing to install directories

Define where is the are located the iproute2 config files.
Get rid of trailing slashes for paths in several file.

Signed-off-by: Christoph J. Thompson <cjsthompson@gmail.com>
diff --git a/Makefile b/Makefile
index 1f6c8bf..c107955 100644
--- a/Makefile
+++ b/Makefile
@@ -1,10 +1,11 @@
-DESTDIR=/usr/
 ROOTDIR=$(DESTDIR)
-LIBDIR=/usr/lib/
+PREFIX=/usr
+LIBDIR=$(PREFIX)/lib
 SBINDIR=/sbin
 CONFDIR=/etc/iproute2
-DOCDIR=/share/doc/iproute2
-MANDIR=/share/man
+DATADIR=$(PREFIX)/share
+DOCDIR=$(DATADIR)/doc/iproute2
+MANDIR=$(DATADIR)/man
 ARPDDIR=/var/lib/arpd
 
 # Path to db_185.h include
@@ -17,6 +18,8 @@
 DEFINES+= -DNO_SHARED_LIBS
 endif
 
+DEFINES+=-DCONFDIR=\"$(CONFDIR)\"
+
 #options if you have a bind>=4.9.4 libresolv (or, maybe, glibc)
 LDLIBS=-lresolv
 ADDLIB=
diff --git a/ip/iplink.c b/ip/iplink.c
index a3613d2..679091e 100644
--- a/ip/iplink.c
+++ b/ip/iplink.c
@@ -34,7 +34,7 @@
 
 #define IPLINK_IOCTL_COMPAT	1
 #ifndef LIBDIR
-#define LIBDIR "/usr/lib/"
+#define LIBDIR "/usr/lib"
 #endif
 
 static void usage(void) __attribute__((noreturn));
diff --git a/tc/Makefile b/tc/Makefile
index f523adc..be8cd5a 100644
--- a/tc/Makefile
+++ b/tc/Makefile
@@ -91,7 +91,7 @@
 LEX := flex
 CFLAGS += -DYY_NO_INPUT
 
-MODDESTDIR := $(DESTDIR)$(patsubst /usr%,%,$(LIBDIR))/tc
+MODDESTDIR := $(DESTDIR)$(LIBDIR)/tc
 
 %.so: %.c
 	$(CC) $(CFLAGS) $(LDFLAGS) -shared -fpic $< -o $@
diff --git a/tc/tc_util.c b/tc/tc_util.c
index 36e3c7d..926ed08 100644
--- a/tc/tc_util.c
+++ b/tc/tc_util.c
@@ -25,7 +25,7 @@
 #include "tc_util.h"
 
 #ifndef LIBDIR
-#define LIBDIR "/usr/lib/"
+#define LIBDIR "/usr/lib"
 #endif
 
 const char *get_tc_lib(void)