blackbox: use install-strip for target install

package/blackbox/blackbox.mk

@@ -10,7 +10,7 @@ BLACKBOX_SITE = http://$(BR2_SOURCEFORGE_MIRROR).dl.sourceforge.net/sourceforge/
 BLACKBOX_AUTORECONF = NO
 BLACKBOX_INSTALL_STAGING = NO
 BLACKBOX_INSTALL_TARGET = YES
-BLACKBOX_INSTALL_TARGET_OPT = DESTDIR=$(TARGET_DIR) install
+BLACKBOX_INSTALL_TARGET_OPT = DESTDIR=$(TARGET_DIR) install-strip
 
 BLACKBOX_CONF_OPT =	--target=$(GNU_TARGET_NAME) --host=$(GNU_TARGET_NAME) \
 		--build=$(GNU_HOST_NAME) --prefix=/usr \