ptpd2: handle snmp optional dep

Handle the optional net-snmp dep or be explicit in disabling it since
since it can pick up a distribution net-snmp-config and pollute
everything. Hopefully fixes:
http://autobuild.buildroot.net/results/5bd/5bdfcf544a83e18d12e27c598084c0ad520d6164/

Signed-off-by: Gustavo Zacarias <gustavo@zacarias.com.ar>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

package/ptpd2/ptpd2.mk

@@ -13,6 +13,13 @@ PTPD2_AUTORECONF = YES
 PTPD2_LICENSE = BSD-2c
 PTPD2_LICENSE_FILES = COPYRIGHT
 
+ifeq ($(BR2_PACKAGE_NETSNMP),y)
+	PTPD2_CONF_ENV += ac_cv_path_PATH_NET_SNMP_CONFIG=$(STAGING_DIR)/usr/bin/net-snmp-config
+	PTPD2_DEPENDENCIES += netsnmp
+else
+	PTPD2_CONF_OPT += --disable-snmp
+endif
+
 define PTPD2_INSTALL_INIT_SYSV
 	$(INSTALL) -m 755 -D package/ptpd2/S65ptpd2 \
 		$(TARGET_DIR)/etc/init.d/S65ptpd2