arp-scan: fix static link when libnl is selected

When libnl is selected, libpcap links with it. Since libpcap doesn't
provide a .pc file and arp-scan doesn't use its libpcap-config script,
we must provide the additional options explicilty.

Fixes
http://autobuild.buildroot.net/results/c605c8cc36348f199a36e2652851b8d02ee222c0

Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

package/arp-scan/arp-scan.mk

@@ -13,6 +13,10 @@ ARP_SCAN_DEPENDENCIES = libpcap
 # 0001-configure-try-linking-to-detect-stack-protector-supp.patch touches acinclude.m4
 ARP_SCAN_AUTORECONF = YES
 
+ifeq ($(BR2_STATIC_LIBS),y)
+ARP_SCAN_CONF_OPTS = LIBS="`$(STAGING_DIR)/usr/bin/pcap-config --static --additional-libs`"
+endif
+
 ARP_SCAN_CONF_ENV = pgac_cv_snprintf_long_long_int_format='%lld'
 
 $(eval $(autotools-package))