configure: add the --libdir option

This commit allows users/packagers to choose a lib directory to store
iproute2 lib files.

At the moment iproute2 ship lib files in /usr/lib and offers no way to
modify this setting. However, according to the FHS, distros may choose
"one or more variants of the /lib directory on systems which support
more than one binary format" (e.g. /usr/lib64 on Fedora).

As Luca states in commit a3272b9372 ("configure: restore backward
compatibility"), packaging systems may assume that 'configure' is from
autotools, and try to pass it some parameters.

Allowing the '--libdir=/path/to/libdir' syntax, we can use this to our
advantage, and let the lib directory to be chosen by the distro
packaging system.

Note that LIBDIR uses "\${prefix}/lib" as default value because autoconf
allows this to be expanded to the --prefix value at configure runtime.
"\${prefix}" is replaced with the PREFIX value in check_lib_dir().

Signed-off-by: Andrea Claudi <aclaudi@redhat.com>
Acked-by: Phil Sutter <phil@nwl.cc>
Signed-off-by: David Ahern <dsahern@kernel.org>

Makefile

@@ -1,6 +1,8 @@
 # SPDX-License-Identifier: GPL-2.0
 # Top level Makefile for iproute2
 
+-include config.mk
+
 ifeq ("$(origin V)", "command line")
 VERBOSE = $(V)
 endif
@@ -13,7 +15,6 @@ MAKEFLAGS += --no-print-directory
 endif
 
 PREFIX?=/usr
-LIBDIR?=$(PREFIX)/lib
 SBINDIR?=/sbin
 CONFDIR?=/etc/iproute2
 NETNS_RUN_DIR?=/var/run/netns
@@ -69,7 +70,7 @@ SUBDIRS=lib ip tc bridge misc netem genl tipc devlink rdma dcb man vdpa
 LIBNETLINK=../lib/libutil.a ../lib/libnetlink.a
 LDLIBS += $(LIBNETLINK)
 
-all: config
+all: config.mk
 	@set -e; \
 	for i in $(SUBDIRS); \
 	do echo; echo $$i; $(MAKE) -C $$i; done
@@ -89,7 +90,7 @@ help:
 	@echo "Make Arguments:"
 	@echo " V=[0|1]             - set build verbosity level"
 
-config:
+config.mk:
 	@if [ ! -f config.mk -o configure -nt config.mk ]; then \
 		sh configure $(KERNEL_INCLUDE); \
 	fi

configure

@@ -4,6 +4,7 @@
 
 INCLUDE="$PWD/include"
 PREFIX="/usr"
+LIBDIR="\${prefix}/lib"
 
 # Output file which is input to Makefile
 CONFIG=config.mk
@@ -149,6 +150,15 @@ EOF
 	rm -f $TMPDIR/ipttest.c $TMPDIR/ipttest
 }
 
+check_lib_dir()
+{
+	LIBDIR=$(echo $LIBDIR | sed "s|\${prefix}|$PREFIX|")
+
+	echo -n "lib directory: "
+	echo "$LIBDIR"
+	echo "LIBDIR:=$LIBDIR" >> $CONFIG
+}
+
 check_ipt()
 {
 	if ! grep TC_CONFIG_XT $CONFIG > /dev/null; then
@@ -487,6 +497,7 @@ usage()
 	cat <<EOF
 Usage: $0 [OPTIONS]
 	--include_dir <dir>		Path to iproute2 include dir
+	--libdir <dir>			Path to iproute2 lib dir
 	--libbpf_dir <dir>		Path to libbpf DESTDIR
 	--libbpf_force <on|off>		Enable/disable libbpf by force. Available options:
 					  on: require link against libbpf, quit config if no libbpf support
@@ -508,6 +519,11 @@ else
 				INCLUDE="$1" ;;
 			--include_dir=*)
 				INCLUDE="${1#*=}" ;;
+			--libdir)
+				shift
+				LIBDIR="$1" ;;
+			--libdir=*)
+				LIBDIR="${1#*=}" ;;
 			--libbpf_dir)
 				shift
 				LIBBPF_DIR="$1" ;;
@@ -544,6 +560,7 @@ if [ "${LIBBPF_FORCE-unused}" != "unused" ]; then
 	fi
 fi
 [ -z "$PREFIX" ] && usage 1
+[ -z "$LIBDIR" ] && usage 1
 
 echo "# Generated config based on" $INCLUDE >$CONFIG
 quiet_config >> $CONFIG
@@ -568,6 +585,7 @@ if ! grep -q TC_CONFIG_NO_XT $CONFIG; then
 fi
 
 echo
+check_lib_dir
 if ! grep -q TC_CONFIG_NO_XT $CONFIG; then
 	echo -n "iptables modules directory: "
 	check_ipt_lib_dir