Adds default for make_num_jobs

Closes https://github.com/netbootxyz/netboot.xyz/issues/1361

roles/netbootxyz/defaults/main.yml

@@ -112,6 +112,7 @@ ipxe_repo: https://github.com/ipxe/ipxe
 ipxe_source_dir: /usr/src/ipxe
 kernel_params: initrd=initrd.magic ${cmdline}
 live_endpoint: https://github.com/netbootxyz
+make_num_jobs: 1
 memdisk_location: http://${boot_domain}/memdisk
 netbootxyz_conf_dir: /etc/netbootxyz
 netbootxyz_root: /var/www/html