create symlinks for usr/lib, too

mk/build.mk

@@ -172,6 +172,7 @@ ${STAGING_TARGET_DIR} ${STAGING_TARGET_DIR}/etc ${STAGING_HOST_DIR}:
 		${STAGING_HOST_DIR}/{bin,lib,usr/bin,usr/lib,usr/include}
 	for i in lib64 lib32 libx32;do \
 		cd ${STAGING_TARGET_DIR}/; ln -sf lib $$i; \
+		cd ${STAGING_TARGET_DIR}/usr; ln -sf lib $$i; \
 	done
 
 ${STAGING_TARGET_DIR}/etc/ipkg.conf: ${STAGING_TARGET_DIR}/etc