package/bitcoin: add optional zeromq dependency

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

package/bitcoin/bitcoin.mk

@@ -25,4 +25,11 @@ else
 BITCOIN_CONF_OPTS += --without-miniupnpc
 endif
 
+ifeq ($(BR2_PACKAGE_ZEROMQ),y)
+BITCOIN_DEPENDENCIES += zeromq
+BITCOIN_CONF_OPTS += --with-zmq
+else
+BITCOIN_CONF_OPTS += --without-zmq
+endif
+
 $(eval $(autotools-package))