Remove dependency on `"golang.org/x/sys/unix"`

[davinci26]

Currently the package "golang.org/x/sys/unix" is used for unix.NETLINK_NETFILTER which makes any project that depends on this library to not be able to compile on a mac which makes it a bit annoying.

I wanted to suggest if we can instead do a little copy paste instead of a lil dependency and hardcode the value of unix.NETLINK_NETFILTER into a const in the library. The value is defined here https://man7.org/linux/man-pages/man7/netlink.7.html https://github.com/torvalds/linux/blob/0031c06807cfa8aa51a759ff8aa09e1aa48149af/include/uapi/linux/netlink.h#L21 so it should never change

[ti-mo]

Hey, thanks for the issue. Fine by me, I typically solve this with an internal/unix package with _linux.go and _other.go files, but that's a little overkill for literally one constant. Agree on the lil dependency, but using the actual constant is good to establish the provenance of the value, and I feel like this type of package should take a dependency on x/sys.

Also note that mdlayher/netlink uses x/sys the same way, so even if fixed here, you still won't be able to build it for the darwin target. I'm curious what your workflow's like or why specifically you need to build for darwin. At least gopls understands the arch differences nowadays and makes all editor features just work.