package/opkg: Add lz4 support

Signed-off-by: Adam Duskett <adam.duskett@amarulasolutions.com>
[yann.morin.1998@free.fr: drop option, use package as condition]
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>

package/opkg/opkg.mk

@@ -22,6 +22,13 @@ else
 OPKG_CONF_OPTS += --disable-gpg
 endif
 
+ifeq ($(BR2_PACKAGE_LZ4),y)
+OPKG_DEPENDENCIES += lz4
+OPKG_CONF_OPTS += --enable-lz4
+else
+OPKG_CONF_OPTS += --disable-lz4
+endif
+
 ifeq ($(BR2_PACKAGE_XZ),y)
 OPKG_DEPENDENCIES += xz
 OPKG_CONF_OPTS += --enable-xz