iproute2: proper detection of libxtables position and flags

Upstream: not sent yet

Any tests involving iptables _MUST_ utilize pkg-config to find the
proper locations of the installation.

configure

@@ -47,7 +47,7 @@ int main(int argc, char **argv)
 
 EOF
 
-if gcc -I$INCLUDE $IPTC -o /tmp/ipttest /tmp/ipttest.c $IPTL -ldl -lxtables >/dev/null 2>&1
+if gcc -I$INCLUDE $IPTC -o /tmp/ipttest /tmp/ipttest.c $IPTL $(pkg-config xtables --cflags --libs) -ldl >/dev/null 2>&1
 then
 	echo "TC_CONFIG_XT:=y" >>Config
 	echo "using xtables"

tc/Makefile

@@ -126,10 +126,10 @@ q_atm.so: q_atm.c
 	$(CC) $(CFLAGS) $(LDFLAGS) -shared -fpic -o q_atm.so q_atm.c -latm
 
 m_xt.so: m_xt.c
-	$(CC) $(CFLAGS) $(LDFLAGS) -shared -fpic -o m_xt.so m_xt.c -lxtables
+	$(CC) $(CFLAGS) $(LDFLAGS) -shared -fpic -o m_xt.so m_xt.c $$(pkg-config xtables --cflags --libs)
 
 m_xt_old.so: m_xt_old.c
-	$(CC) $(CFLAGS) $(LDFLAGS) -shared -fpic -o m_xt_old.so m_xt_old.c -lxtables
+	$(CC) $(CFLAGS) $(LDFLAGS) -shared -fpic -o m_xt_old.so m_xt_old.c $$(pkg-config xtables --cflags --libs)
 
 %.yacc.c: %.y
 	$(YACC) $(YACCFLAGS) -o $@ $<