zeromq: add explicit --without-pgm when pgm is disabled

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

package/zeromq/zeromq.mk

@@ -38,6 +38,8 @@ endif
 ifeq ($(BR2_PACKAGE_ZEROMQ_PGM),y)
 ZEROMQ_DEPENDENCIES += host-pkgconf openpgm
 ZEROMQ_CONF_OPTS += --with-pgm
+else
+ZEROMQ_CONF_OPTS += --without-pgm
 endif
 
 # ZeroMQ uses libsodium if it's available.