NETLINK is going to replace rtsock and a number of other ioctl/sysctl interfaces. In-base utilies such as route(8), netstat(8) and soon ifconfig(8) are being converted to use netlink sockets as a transport between kenel and userland.
In the current configuration, it still possible have the kernel without NETLINK (`nooptions NETLINK`) and use the aforementioned utilies by buidling the world with `WITHOUT_NETLINK` src.conf knob. However, this approach does not cover the cases when person unintentionally builds a custom kernel without netlink and tries to use the standard userland.
This change adds `option NETLINK` to the default options for each architecture, fixing the custom kernel issue.
For now, arm w/ std.armv6 still builds without NETLINK.