package/iputils: fix build without NLS

Set USE_GETTEXT depending on BR2_SYSTEM_ENABLE_NLS as otherwise build
will fail if gettext is not installed on host because USE_GETTEXT is
enabled by default since version 20190324 and
https://github.com/iputils/iputils/commit/2615a527209bb408b54028ef6405075cadd4541b

Fixes:
 - http://autobuild.buildroot.org/results/127823ddbd75336abc0fe0e9bd11e4f5249df87c

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Acked-by: Petr Vorel <petr.vorel@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

package/iputils/iputils.mk

@@ -49,6 +49,12 @@ IPUTILS_CONF_OPTS += -DUSE_CRYPTO=none
 IPUTILS_CONF_OPTS += -DBUILD_NINFOD=false
 endif
 
+ifeq ($(BR2_SYSTEM_ENABLE_NLS),y)
+IPUTILS_CONF_OPTS += -DUSE_GETTEXT=true
+else
+IPUTILS_CONF_OPTS += -DUSE_GETTEXT=false
+endif
+
 IPUTILS_CONF_OPTS += -DBUILD_TRACEROUTE6=true
 
 # XSL Stylesheets for DocBook 5 not packaged for buildroot