avahi: move libdns_sd compat hook definition inside conditional block

As directed in the buildroot manual, "Optional hooks: keep hook
definition and assignment together in one if block".  And also
to be consistent with the rest of avahi.mk.

Signed-off-by: Danomi Manchego <danomimanchego123@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

package/avahi/avahi.mk

@@ -216,13 +216,13 @@ define AVAHI_INSTALL_INIT_SYSV
 	$(AVAHI_INSTALL_DAEMON_INIT_SYSV)
 endef
 
+ifeq ($(BR2_PACKAGE_AVAHI_LIBDNSSD_COMPATIBILITY),y)
 # applications expects to be able to #include <dns_sd.h>
 define AVAHI_STAGING_INSTALL_LIBDNSSD_LINK
 	ln -sf avahi-compat-libdns_sd/dns_sd.h \
 		$(STAGING_DIR)/usr/include/dns_sd.h
 endef
 
-ifeq ($(BR2_PACKAGE_AVAHI_LIBDNSSD_COMPATIBILITY),y)
 AVAHI_POST_INSTALL_STAGING_HOOKS += AVAHI_STAGING_INSTALL_LIBDNSSD_LINK
 endif